Blue-emitting nanocrystals with cubic shape and fluoride passivation

ABSTRACT

This disclosure pertains to the field of nanotechnology. The disclosure provides methods of preparing nanostructures with fluoride passivation. The disclosure also provides methods of preparing nanostructures with fluoride and amine passivation. The nanostructures have high quantum yield, narrow emission peak width, tunable emission wavelength, and colloidal stability. Also provided are nanostructures prepared using the methods. And, nanostructure films and molded articles comprising the nanostructures are also provided.

FIELD OF THE INVENTION Field of the Invention

This disclosure pertains to the field of nanotechnology. The disclosureprovides methods of preparing nanostructures with fluoride passivation.The disclosure also provides methods of preparing nanostructures withfluoride and amine passivation. The nanostructures have high quantumyield, narrow emission peak width, tunable emission wavelength, andcolloidal stability. Also provided are nanostructures prepared using themethods. And, nanostructure films and molded articles comprising thenanostructures are also provided.

Background Art

Semiconductor nanostructures can be incorporated into a variety ofelectronic and optical devices. The electrical and optical properties ofsuch nanostructures vary, e.g., depending on their composition, shape,and size. For example, size-tunable properties of semiconductornanoparticles are of great interest for applications such as lightemitting diodes (LEDs) and liquid crystal displays (LCDs). Highlyluminescent nanostructures are particularly desirable for suchapplications.

Steric bulk of long-chain alkyl ligands can result in insufficientligand coverage on the surface of semiconductor nanocrystals due topacking limitation. Similarly, rounded particle surfaces exhibit steps,pits, and kinks that can be difficult to passivate with ligands. Suchunpassivated sites on the surface of quantum dots can lead to mid-gapstates that act as hole traps when an electric potential is appliedacross the quantum dots. Holes will accumulate at the HTL-QD interfaceleading to a rise in operating voltage and irreversible electrochemicaldegradation.

The native ligand set (e.g., carboxylates and phosphines) of mostquantum dots is hydrophobic and thus quantum dots comprising thesenative ligands are not soluble in a wide range of organic media and areincompatible with matrix materials commonly used in the preparation ofquantum dots films. Ligand exchange can be used to solve these problemsbut the exchange may influence surface trap states and hence, thephotoluminescence quantum yield of the quantum dots. For example, metalcarboxylate complexes were readily displaced from carboxylate-terminatedME complexes (ME=CdSe, CdS, PbSe, or PbS) using various Lewis bases(Anderson, N.C., et al., J. Am. Chem. Soc. 135:18536-18548 (2013)).However, it was found that removal of up to 90% of surface-boundCd(O₂CR)₂ (R=oleyl or tetradecyl) from CdSe and CdS nanocrystalsresulted in a decrease in the photoluminescence quantum yield from 10%to <1% for CdSe nanocrystals and from 20% to <1 for CdS nanocrystals.Hence, it was found that photoluminescence quantum yield and ligationwere not simply related, not only because of their nonlinearindependence, but also because Cd(O₂CR)₂ can concurrently be displacedwith amine binding.

A need exists to produce nanostructures that have high quantum yield,narrow emission peak width, tunable emission wavelength, and colloidalstability.

BRIEF SUMMARY OF THE INVENTION

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising a nanocrystal core; and at least one shelldisposed on the core, wherein at least one shell comprises ZnS andfluoride.

In some embodiments, the core comprises ZnSe, ZnSeTe, InP, or InAs. Insome embodiments, the core comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1.

In some embodiments, the nanostructure comprises two shells. In someembodiments, at least one shell comprises ZnSe. In some embodiments, atleast one shell comprises ZnSe and fluoride. In some embodiments, the atleast one shell comprises a first shell comprising ZnSe and a secondshell comprising ZnS and fluoride. In some embodiments, the at least oneshell comprises a first shell comprising ZnSe and fluoride, and a secondshell comprising ZnS and fluoride.

In some embodiments, the fluoride is in the form of a metal fluoride,ammonium fluoride or tetraalkylammonium fluoride. In some embodiments,the fluoride is in the form of a metal fluoride comprising ZnF₂, HfF₄,or ZrF₄. In some embodiments, the metal fluoride is ZnF₂.

In some embodiments, at least one shell comprises ZnS and ZnF₂. In someembodiments, at least one shell comprises ZnSe and ZnF₂.

In some embodiments, the fluoride is in the form of a tetraalkylammoniumfluoride comprising tetrabutylammonium fluoride, tetrapropylammoniumfluoride, diisopropyldimethylammonium fluoride, tetraethylammoniumfluoride, and tetramethylammonium fluoride, dioctadecyldimethylammoniumfluoride, dihexadecyldimethylammonium fluoride,ditetradecyldimethylammonium fluoride, didodecyldimethylammoniumfluoride, didecyldimethylammonium fluoride, dioctyldimethylammoniumfluoride, bis(ethylhexyl)dimethylammonium fluoride,octadecyltrimethylammonium fluoride, oleyltrimethylammonium fluoride,hexadecyltrimethylammonium fluoride, tetradecyltrimethylammoniumfluoride, dodecyltrimethylammonium fluoride, decyltrimethylammoniumfluoride, octyltrimethylammonium fluoride, phenylethyltrimethylammoniumfluoride, benzyltrimethylammonium fluoride, phenyltrimethylammoniumfluoride, benzylhexadecyldimethylammonium fluoride,benzyltetradecyldimethylammonium fluoride, benzyldodecyldimethylammoniumfluoride, benzyldecyldimethylammonium fluoride,benzyloctyldimethylammonium fluoride, benzyltributylammonium fluoride,or benzyltriethylammonium fluoride. In some embodiments, thetetraalkylammonium fluoride is tetrabutylammonium fluoride.

In some embodiments, the molar ratio of fluoride bound to thenanostructure to zinc in the nanostructure is between about 0.05 andabout 0.33.

In some embodiments, the molar ratio of fluoride bound to thenanostructure to zinc in the nanostructure is about 0.13. In someembodiments, the molar ratio of fluoride bound to the nanostructure tozinc in the nanostructure is about 0.32.

In some embodiments, the nanostructure further comprises a solvent. Insome embodiments, the solvent is a non-polar solvent. In someembodiments, the non-polar solvent comprises hexane, heptane, octane,toluene, or mixtures thereof. In some embodiments, the non-polar solventis octane. In some embodiments, the non-polar solvent is hexane.

In some embodiments, the nanostructure exhibits a photoluminescencequantum yield of between about 60% and about 99%. In some embodiments,the nanostructure exhibits a photoluminescence quantum yield of betweenabout 70% and about 99%.

In some embodiments, the nanostructure comprises a core comprising ZnSe,and at least one shell comprising ZnS and ZnF₂. In some embodiments, thenanostructure comprises a core comprising ZnSe, at least one shellcomprising ZnSe, and at least one shell comprising ZnS and ZnF₂. In someembodiments, the nanostructure comprises a core comprising ZnSe, atleast one shell comprising ZnSe and ZnF₂, and at least one shellcomprising ZnS and ZnF₂. In some embodiments, the nanostructurecomprises a core comprising ZnSe_(1-x)Te_(x), wherein 0≤x<1, and atleast one shell comprising ZnS and ZnF₂. In some embodiments, thenanostructure comprises a core comprising ZnSe_(1-x)Te_(x), wherein0≤x<1, at least one shell comprising ZnSe, and at least one shellcomprising ZnS and ZnF₂. In some embodiments, the nanostructurecomprises a core comprising ZnSe_(1-x)Te_(x), wherein 0≤x<1, at leastone shell comprising ZnSe and ZnF₂, and at least one shell comprisingZnS and ZnF₂.

In some embodiments, the nanostructure is a quantum dot. In someembodiments, the nanostructure is substantially cubic in shape.

In some embodiments, the present disclosure provides a method ofpreparing a nanostructure, comprising:

-   -   (a) providing a nanocrystal core;    -   (b) optionally admixing the core in (a) with a zinc source and a        selenium source to provide a core with a ZnSe shell;    -   (c) admixing the core in (a) or the core with a ZnSe shell        in (b) with a fluoride source; and    -   (d) infusing a solution comprising a zinc source and a sulfur        source into the admixture in (c);        to provide the nanostructure.

In some embodiments, the core comprises ZnSe, ZnSeTe, InP, or InAs. Insome embodiments, the core comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1. Insome embodiments, the core comprises ZnSe.

In some embodiments, the admixing in (b) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the admixing in (b)is at a temperature of about 310° C.

In some embodiments, the admixing in (b) comprises admixing the core in(a) with a zinc source, a selenium source, and optionally a fluoridesource to provide a core with a shell comprising ZnSe and fluoride. Insome embodiments, the fluoride source comprises a metal fluoride, NH₄F,or a tetraalkylammonium fluoride. In some embodiments, the fluoridesource is a metal fluoride comprising ZnF₂, HfF₄, or ZrF₄. In someembodiments, the fluoride source in is ZnF₂.

In some embodiments, the admixing in (c) is at a temperature betweenabout 70° C. and about 130° C. In some embodiments, the admixing in (c)is at a temperature of about 100° C.

In some embodiments, the infusing in (d) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the infusing in (d)is at a temperature between is at a temperature of about 310° C.

In some embodiments, the infusing in (d) is at an infusing rate betweenabout 0.05 mL/min and about 2.0 mL/min. In some embodiments, theinfusing in (d) is at an infusing rate of about 0.1 mL/min.

In some embodiments, the selenium source in (b) comprisestrioctylphosphine selenide, tri(n-butyl)phosphine selenide,tri(sec-butyl)phosphine selenide, tri(tert-butyl)phosphine selenide,trimethylphosphine selenide, triphenylphosphine selenide,diphenylphosphine selenide, phenylphosphine selenide,cyclohexylphosphine selenide, octaselenol, dodecaselenol, selenophenol,elemental selenium, hydrogen selenide, bis(trimethylsilyl) selenide, ormixtures thereof. In some embodiments, the selenium source in (b) istrioctylphosphine selenide.

In some embodiments, the zinc source in (b) comprises diethylzinc,dimethylzinc, zinc acetate, zinc acetylacetonate, zinc iodide, zincbromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide,zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate,zinc sulfate, zinc hexanoate, zinc octanoate, zinc laurate, zincmyristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, ormixtures thereof. In some embodiments, the zinc source in (b) is zincoleate.

In some embodiments, the fluoride source in (c) comprises a metalfluoride, NH₄F, or a tetraalkylammonium fluoride. In some embodiments,the fluoride source in (c) is a metal fluoride comprising ZnF₂, HfF₄, orZrF₄. In some embodiments, the fluoride source in (c) is ZnF₂.

In some embodiments, the zinc source in (d) comprises diethylzinc,dimethylzinc, zinc acetate, zinc acetylacetonate, zinc iodide, zincbromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide,zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate,zinc sulfate, zinc hexanoate, zinc octanoate, zinc laurate, zincmyristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, ormixtures thereof. In some embodiments, the zinc source in (d) is zincoleate.

In some embodiments, the sulfur source in (d) comprisestrioctylphosphine sulfide, elemental sulfur, octanethiol, dodecanethiol,octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate,α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan,bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, or combinationsthereof. In some embodiments, the sulfur source in (d) istrioctylphosphine sulfide.

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising ZnSe or ZnSe_(1-x)Te_(x), wherein 0≤x<1,and a first metal fluoride; and at least one shell disposed on the core,wherein at least one shell comprises ZnS and optionally a second metalfluoride.

In some embodiments, the core comprises ZnSe. In some embodiments, thecore comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1.

In some embodiments, the nanostructure comprises two shells.

In some embodiments, the first metal fluoride comprises ZnF₂, HfF₄, orZrF₄. In some embodiments, the first metal fluoride is ZrF₄.

In some embodiments, the second metal fluoride comprises ZnF₂, HfF₄, orZrF₄. In some embodiments, the second metal fluoride is ZrF₄.

In some embodiments, at least one shell comprises ZnS and ZrF₄.

In some embodiments, the molar ratio of fluoride in the nanostructure tozinc in the nanostructure is between about 0.05 and about 0.35.

In some embodiments, the nanostructure further comprises a solvent. Insome embodiments, the solvent is a non-polar solvent. In someembodiments, the non-polar solvent comprises hexane, heptane, octane,toluene, or mixtures thereof. In some embodiments, the non-polar solventis octane. In some embodiments, the non-polar solvent is hexane.

In some embodiments, the nanostructure exhibits a photoluminescencequantum yield of between about 60% and about 99%. In some embodiments,the nanostructure exhibits a photoluminescence quantum yield of betweenabout 70% and about 99%.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride comprising ZnF₂, HfF₄, or ZrF₄; and at least oneshell comprising ZnS and a metal fluoride comprising ZnF₂, HfF₄, orZrF₄.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride comprising ZnF₂, HfF₄, or ZrF₄; at least one shellcomprising ZnSe, and at least one shell comprising ZnS and a metalfluoride comprising ZnF₂, HfF₄, or ZrF₄.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride comprising ZnF₂, HfF₄, and ZrF₄; and at least oneshell comprising ZnS.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride comprising ZnF₂, HfF₄, or ZrF₄; at least one shellcomprising ZnSe; and at least one shell comprising ZnS.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride comprising ZnF₂,HfF₄, or ZrF₄; and at least one shell comprising ZnS and a metalfluoride comprising ZnF₂, HfF₄, or ZrF₄.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride comprising ZnF₂,HfF₄, or ZrF₄; at least one shell comprising ZnSe; and at least oneshell comprising ZnS and a metal fluoride comprising ZnF₂, HfF₄, orZrF₄.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride comprising ZnF₂,HfF₄, or ZrF₄; and at least one shell comprising ZnS.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride comprising ZnF₂,HfF₄, or ZrF₄; at least one shell comprising ZnSe; and at least oneshell comprising ZnS.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the nanostructure is substantially cubic in shape.

In some embodiments, the present disclosure provides a method ofpreparing a nanostructure, comprising:

-   -   (a) admixing a solution of a zinc source, a selenium source, and        a first metal fluoride source to provide a core comprising ZnSe        or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and the first metal        fluoride;    -   (b) optionally admixing the core in (a) with a zinc source and a        selenium source to provide a core with a ZnSe shell;    -   (c) optionally admixing the core in (a) or the core with a ZnSe        shell in (b) with a second metal fluoride source; and    -   (d) infusing a solution comprising a zinc source and a sulfur        source into the admixture in (a), (b), or (c);        to provide a nanostructure.

In some embodiments, the admixing in (a) is at a temperature betweenabout 20° C. and about 120° C. In some embodiments, the admixing in (a)is at a temperature of about 100° C.

In some embodiments, the admixing in (b) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the admixing in (b)is at a temperature of about 310° C.

In some embodiments, the admixing in (c) is at a temperature betweenabout 20° C. and about 120° C. In some embodiments, the admixing in (c)is at a temperature of about 100° C.

In some embodiments, the infusing in (d) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the infusing in (d)is at a temperature of about 310° C.

In some embodiments, the infusing in (d) is at an infusing rate betweenabout 0.05 mL/min and about 5.0 mL/min. In some embodiments, theinfusing in (d) is at an infusing rate of about 0.5 mL/min.

In some embodiments, the selenium source in (a) comprisestrioctylphosphine selenide, tri(n-butyl)phosphine selenide,tri(sec-butyl)phosphine selenide, tri(tert-butyl)phosphine selenide,trimethylphosphine selenide, triphenylphosphine selenide,diphenylphosphine selenide, phenylphosphine selenide,cyclohexylphosphine selenide, octaselenol, dodecaselenol, selenophenol,elemental selenium, hydrogen selenide, bis(trimethylsilyl) selenide, ormixtures thereof. In some embodiments, the selenium source in (a) istrioctylphosphine selenide.

In some embodiments, the zinc source in (a) comprises diethylzinc,dimethylzinc, zinc acetate, zinc acetylacetonate, zinc iodide, zincbromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide,zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate,zinc sulfate, zinc hexanoate, zinc octanoate, zinc laurate, zincmyristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, ormixtures thereof. In some embodiments, the zinc source in (a) is zincoleate.

In some embodiments, the first metal fluoride in (a) comprises ZnF₂,HfF₄, or ZrF₄. In some embodiments, the first metal fluoride source in(a) is ZnF₂. In some embodiments, the first metal fluoride source in (a)is HfF₄. In some embodiments, the first metal fluoride source in (a) isZrF₄.

In some embodiments, the zinc source in (b) comprises diethylzinc,dimethylzinc, zinc acetate, zinc acetylacetonate, zinc iodide, zincbromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide,zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate,zinc sulfate, zinc hexanoate, zinc octanoate, zinc laurate, zincmyristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, ormixtures thereof. In some embodiments, the zinc source in (b) is zincoleate.

In some embodiments, the selenium source in (b) comprisestrioctylphosphine selenide, tri(n-butyl)phosphine selenide,tri(sec-butyl)phosphine selenide, tri(tert-butyl)phosphine selenide,trimethylphosphine selenide, triphenylphosphine selenide,diphenylphosphine selenide, phenylphosphine selenide,cyclohexylphosphine selenide, octaselenol, dodecaselenol, selenophenol,elemental selenium, hydrogen selenide, bis(trimethylsilyl) selenide, ormixtures thereof. In some embodiments, the selenium source in (b) istrioctylphosphine selenide.

In some embodiments, the second metal fluoride in (c) comprises ZnF₂,HfF₄, or ZrF₄. In some embodiments, the second metal fluoride source in(c) is ZnF₂. In some embodiments, the second metal fluoride source in(c) is HfF₄. In some embodiments, the second metal fluoride source in(c) is ZrF₄.

In some embodiments, the zinc source in (d) comprises diethylzinc,dimethylzinc, zinc acetate, zinc acetylacetonate, zinc iodide, zincbromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide,zinc nitrate, zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate,zinc sulfate, zinc hexanoate, zinc octanoate, zinc laurate, zincmyristate, zinc palmitate, zinc stearate, zinc dithiocarbamate, ormixtures thereof. In some embodiments, the zinc source in (d) is zincoleate.

In some embodiments, the sulfur source in (d) comprisestrioctylphosphine sulfide, elemental sulfur, octanethiol, dodecanethiol,octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate,α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan,bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, or combinationsthereof. In some embodiments, the sulfur source in (d) istrioctylphosphine sulfide.

In some embodiments, the present disclosure provides a device comprisingthe nanostructure of the present disclosure. In some embodiments, thedevice is a display device.

In some embodiments, the display device comprises a quantum dot colorconverter comprising:

-   -   a back plane;    -   a display panel disposed on the back plane; and    -   a patterned quantum dot layer comprising the nanostructure, the        patterned quantum dot layer disposed on the display panel.

In some embodiments, the backplane comprises a blue LED, an LCD, anOLED, or a microLED.

In some embodiments, the present disclosure provides a nanostructurefilm comprising at least one population of nanostructures, thenanostructures comprising a core comprising a nanocrystal core; and atleast one shell disposed on the core, wherein at least one shellcomprises ZnS and fluoride.

In some embodiments, the present disclosure provides a nanostructurefilm comprising at least one population of nanostructures, thenanostructures comprising a core comprising ZnSe or ZnSe_(1-x)Te_(x),wherein 0≤x<1, and a first metal fluoride; and at least one shelldisposed on the core, wherein at least one shell comprises ZnS andoptionally a second metal fluoride.

In some embodiments, the nanostructure film further comprises at leastone organic resin. In some embodiments, the nanostructure film comprisesbetween one and five organic resins. In some embodiments, thenanostructure film comprises one organic resin. In some embodiments, theat least one organic resin is a thermosetting resin or a UV curableresin. In some embodiments, the at least one organic resin is a UVcurable resin.

In some embodiments, the present disclosure provides a molded articlecomprising the nanostructure film.

In some embodiments, the molded article comprising:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising a        nanocrystal core; and at least one shell disposed on the core,        wherein at least one shell comprises ZnS and fluoride.

In some embodiments, the molded article comprising:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising ZnSe        or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and a first metal fluoride;        and at least one shell disposed on the core, wherein at least        one shell comprises ZnS and optionally a second metal fluoride.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the molded article is an electroluminescent device.In some embodiments, the molded article is a light emitting diode. Insome embodiments, the molded article is a liquid crystal display.

In some embodiments, the maximum external quantum efficiency (EQE) ofthe electroluminescent device is between about 1.5% and about 15%.

In some embodiments, the maximum external quantum efficiency (EQE) ofthe electroluminescent device is about 5%.

In some embodiments, the electroluminescent device reaches 50% ofinitial luminance of 500 cd/m² (nits) after between about 19 seconds andabout 35 seconds.

In some embodiments, the time for the electroluminescent device to reach50% of initial luminance of 500 cd/m² (nits) (T50) is at least aboutthree times longer than the T50 for an electroluminescent devicecomprising the corresponding nanostructure without any fluoride in theshell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of the density of states diagram with the midgaptrap states indicated as “trap states.” Full surface coverage by halideions reduces the midgap trap states, forming a better electronicallybalanced quantum dot.

FIG. 2 is a transmission electron microscopy (TEM) image showing thetypical quasi-spherical morphology that is typical of ZnSe/ZnScore/shell structured quantum dots.

FIG. 3 is a TEM image showing an increased ratio of tetrahedral andcubic particles due to the synthesis of ZnSe/ZnS core/shell structurequantum dots treated with 4 mol. eq. ZnF₂.

FIG. 4 is a TEM image showing an increased ratio of tetrahedral andcubic particles due to the synthesis of ZnSe/ZnS core/shell structurequantum dots with 14 mol. eq. ZnF₂.

FIG. 5 is a TEM image showing the typical quasi-spherical morphologythat is typical of ZnSeTe/ZnSe/ZnS core/shell/shell structured quantumdots.

FIG. 6 is a TEM image showing an increased ratio of tetrahedral andcubic particles due to the synthesis of ZnSeTe/ZnSe/ZnS core/shell/shellstructured quantum dots using ZnF₂.

FIG. 7 is a scatterplot of external quantum efficiency (EQE) versusluminance (nits) for ZnSe/ZnS quantum dots with standard ligands (noZnF₂) (●), ZnSe/ZnS quantum dots treated with 4 mol. eq. ZnF₂ (▴), andZnSe/ZnS quantum dots treated with 14 mol. eq. ZnF₂ (▪)

FIG. 8 is an X-ray photoelectron spectroscopy (XPS) survey spectrum ofZnSe/ZnS quantum dots treated with ZnF₂.

FIGS. 9A and 9B show high resolution XPS spectra of the fluorine Isregion comparing a standard ZnSe/ZnS quantum dot with no ZnF₂ (FIG. 9A)to a ZnSe/ZnS quantum dot treated with ZnF₂.

FIG. 10 is a table comparing solution quantum yield, maximum externalquantum efficiency and device lifetime for a control ZnSe/ZnS quantumdot, ZnSe/ZnS quantum dots containing metal fluorides in only the shelllayer, ZnSe/ZnS quantum dots containing metal fluorides in only the corelayer, and ZnSe quantum dots containing metal fluorides in both the corelayer and the shell layer.

FIG. 11 are bar graphs showing the photoluminescence intensity forInP/ZnSe/ZnS quantum dots comprising 5 different ZnSe and ZnS shellthicknesses (4.5 monolayers of ZnSe and 2.5 monolayers of ZnS; 2.5monolayers of ZnSe and 6.5 monolayers of ZnS; 2.5 monolayers of ZnSe and2.5 monolayers of ZnS; 3.5 monolayers of ZnSe and 4.5 monolayers of ZnS;and 3.5 monolayers of ZnSe and 4.5 monolayers of ZnS (on an etched InPcore)) after addition of dodecylamine at three different concentrations:0 μL, 5 μL, and 20 μL.

FIG. 12 is a schematic showing L-promoted Z-type ligand displacementwhere a neutral Lewis base ligand (L), such as an amine, readilydisplaces a metal carboxylate (MX₂, where M is Cd or Pb; X is O₂CR, Cl,or SR; and R is C₁₋₂₀ alkyl or oleyl) from carboxylate-terminated CdS,CdSe, PbS, or PbSe quantum dots.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention pertains. The following definitionssupplement those in the art and are directed to the current applicationand are not to be imputed to any related or unrelated case, e.g., to anycommonly owned patent or application. Although any methods and materialssimilar or equivalent to those described herein can be used in thepractice for testing of the present invention, the preferred materialsand methods are described herein. Accordingly, the terminology usedherein is for the purpose of describing particular embodiments only, andis not intended to be limiting.

As used in this specification and the appended claims, the singularforms “a,” “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “ananostructure” includes a plurality of such nanostructures, and thelike.

The term “about” as used herein indicates the value of a given quantityvaries by ±10% of the value. For example, “about 100 nm” encompasses arange of sizes from 90 nm to 110 nm, inclusive.

A “nanostructure” is a structure having at least one region orcharacteristic dimension with a dimension of less than about 500 nm. Insome embodiments, the nanostructure has a dimension of less than about200 nm, less than about 100 nm, less than about 50 nm, less than about20 nm, or less than about 10 nm. Typically, the region or characteristicdimension will be along the smallest axis of the structure. Examples ofsuch structures include nanowires, nanorods, nanotubes, branchednanostructures, nanotetrapods, nanotripods, nanobipods, nanocrystals,nanodots, quantum dots, nanoparticles, and the like. Nanostructures canbe, e.g., substantially crystalline, substantially monocrystalline,polycrystalline, amorphous, or a combination thereof. In someembodiments, each of the three dimensions of the nanostructure has adimension of less than about 500 nm, less than about 200 nm, less thanabout 100 nm, less than about 50 nm, less than about 20 nm, or less thanabout 10 nm.

The term “heterostructure” when used with reference to nanostructuresrefers to nanostructures characterized by at least two different and/ordistinguishable material types. Typically, one region of thenanostructure comprises a first material type, while a second region ofthe nanostructure comprises a second material type. In certainembodiments, the nanostructure comprises a core of a first material andat least one shell of a second (or third etc.) material, where thedifferent material types are distributed radially about the long axis ofa nanowire, a long axis of an arm of a branched nanowire, or the centerof a nanocrystal, for example. A shell can, but need not, completelycover the adjacent materials to be considered a shell or for thenanostructure to be considered a heterostructure; for example, ananocrystal characterized by a core of one material covered with smallislands of a second material is a heterostructure. In other embodiments,the different material types are distributed at different locationswithin the nanostructure; e.g., along the major (long) axis of ananowire or along a long axis of arm of a branched nanowire. Differentregions within a heterostructure can comprise entirely differentmaterials, or the different regions can comprise a base material (e.g.,silicon) having different dopants or different concentrations of thesame dopant.

As used herein, the “diameter” of a nanostructure refers to the diameterof a cross-section normal to a first axis of the nanostructure, wherethe first axis has the greatest difference in length with respect to thesecond and third axes (the second and third axes are the two axes whoselengths most nearly equal each other). The first axis is not necessarilythe longest axis of the nanostructure; e.g., for a disk-shapednanostructure, the cross-section would be a substantially circularcross-section normal to the short longitudinal axis of the disk. Wherethe cross-section is not circular, the diameter is the average of themajor and minor axes of that cross-section. For an elongated or highaspect ratio nanostructure, such as a nanowire, the diameter is measuredacross a cross-section perpendicular to the longest axis of thenanowire. For a spherical nanostructure, the diameter is measured fromone side to the other through the center of the sphere.

The terms “crystalline” or “substantially crystalline,” when used withrespect to nanostructures, refer to the fact that the nanostructurestypically exhibit long-range ordering across one or more dimensions ofthe structure. It will be understood by one of skill in the art that theterm “long range ordering” will depend on the absolute size of thespecific nanostructures, as ordering for a single crystal cannot extendbeyond the boundaries of the crystal. In this case, “long-rangeordering” will mean substantial order across at least the majority ofthe dimension of the nanostructure. In some instances, a nanostructurecan bear an oxide or other coating, or can be comprised of a core and atleast one shell. In such instances it will be appreciated that theoxide, shell(s), or other coating can but need not exhibit such ordering(e.g. it can be amorphous, polycrystalline, or otherwise). In suchinstances, the phrase “crystalline,” “substantially crystalline,”“substantially monocrystalline,” or “monocrystalline” refers to thecentral core of the nanostructure (excluding the coating layers orshells). The terms “crystalline” or “substantially crystalline” as usedherein are intended to also encompass structures comprising variousdefects, stacking faults, atomic substitutions, and the like, as long asthe structure exhibits substantial long range ordering (e.g., order overat least about 80% of the length of at least one axis of thenanostructure or its core). In addition, it will be appreciated that theinterface between a core and the outside of a nanostructure or between acore and an adjacent shell or between a shell and a second adjacentshell can contain non-crystalline regions and can even be amorphous.This does not prevent the nanostructure from being crystalline orsubstantially crystalline as defined herein.

The term “monocrystalline” when used with respect to a nanostructureindicates that the nanostructure is substantially crystalline andcomprises substantially a single crystal. When used with respect to ananostructure heterostructure comprising a core and one or more shells,“monocrystalline” indicates that the core is substantially crystallineand comprises substantially a single crystal.

A “nanocrystal” is a nanostructure that is substantiallymonocrystalline. A nanocrystal thus has at least one region orcharacteristic dimension with a dimension of less than about 500 nm. Insome embodiments, the nanocrystal has a dimension of less than about 200nm, less than about 100 nm, less than about 50 nm, less than about 20nm, or less than about 10 nm. The term “nanocrystal” is intended toencompass substantially monocrystalline nanostructures comprisingvarious defects, stacking faults, atomic substitutions, and the like, aswell as substantially monocrystalline nanostructures without suchdefects, faults, or substitutions. In the case of nanocrystalheterostructures comprising a core and one or more shells, the core ofthe nanocrystal is typically substantially monocrystalline, but theshell(s) need not be. In some embodiments, each of the three dimensionsof the nanocrystal has a dimension of less than about 500 nm, less thanabout 200 nm, less than about 100 nm, less than about 50 nm, less thanabout 20 nm, or less than about 10 nm.

The term “quantum dot” (or “dot”) refers to a nanocrystal that exhibitsquantum confinement or exciton confinement. Quantum dots can besubstantially homogenous in material properties, or in certainembodiments, can be heterogeneous, e.g., including a core and at leastone shell. The optical properties of quantum dots can be influenced bytheir particle size, chemical composition, and/or surface composition,and can be determined by suitable optical testing available in the art.The ability to tailor the nanocrystal size, e.g., in the range betweenabout 1 nm and about 15 nm, enables photoemission coverage in the entireoptical spectrum to offer great versatility in color rendering.

A “ligand” is a molecule capable of interacting (whether weakly orstrongly) with one or more faces of a nanostructure, e.g., throughcovalent, ionic, van der Waals, or other molecular interactions with thesurface of the nanostructure.

“Photoluminescence quantum yield” is the ratio of photons emitted tophotons absorbed, e.g., by a nanostructure or population ofnanostructures. As known in the art, quantum yield is typicallydetermined by a comparative method using well-characterized standardsamples with known quantum yield values.

As used herein, the term “monolayer” is a measurement unit of shellthickness derived from the bulk crystal structure of the shell materialas the closest distance between relevant lattice planes. By way ofexample, for cubic lattice structures the thickness of one monolayer isdetermined as the distance between adjacent lattice planes in the [111]direction. By way of example, one monolayer of cubic ZnSe corresponds to0.33 nm and one monolayer of cubic ZnS corresponds to 0.31 nm thickness.The thickness of a monolayer of alloyed materials can be determined fromthe alloy composition through Vegard's law.

As used herein, the term “shell” refers to material deposited onto thecore or onto previously deposited shells of the same or differentcomposition and that result from a single act of deposition of the shellmaterial. The exact shell thickness depends on the material as well asthe precursor input and conversion and can be reported in nanometers ormonolayers. As used herein, “target shell thickness” refers to theintended shell thickness used for calculation of the required precursoramount. As used herein, “actual shell thickness” refers to the actuallydeposited amount of shell material after the synthesis and can bemeasured by methods known in the art. By way of example, actual shellthickness can be measured by comparing particle diameters determinedfrom TEM images of nanocrystals before and after a shell synthesis.

As used herein, the term “full width at half-maximum” (FWHM) is ameasure of the size distribution of quantum dots. The emission spectraof quantum dots generally have the shape of a Gaussian curve. The widthof the Gaussian curve is defined as the FWHM and gives an idea of thesize distribution of the particles. A smaller FWHM corresponds to anarrower quantum dot nanocrystal size distribution. FWHM is alsodependent upon the emission wavelength maximum.

“Peak emission wavelength” (PWL) is the wavelength where the radiometricemission spectrum of the light source reaches its maximum.

As used herein, the term “external quantum efficiency” (EQE) is a ratioof the number of photons emitted from a light emitting diode (LED) tothe number of electrons passing through the device. The EQE measures howefficiently a LED converts electrons to photons and allows them toescape. EQE can be measured using the formula:

EQE=[injection efficiency]×[solid-state quantum yield]×[extractionefficiency]

where:

-   -   injection efficiency=the proportion of electrons passing through        the device that are injected into the active region;    -   solid-state quantum yield=the proportion of all electron-hole        recombinations in the active region that are radiative and thus,        produce photons; and    -   extraction efficiency=the proportion of photons generated in the        active region that escape from the device.

Unless clearly indicated otherwise, ranges listed herein are inclusive.

A variety of additional terms are defined or otherwise characterizedherein.

Nanostructure

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising a nanocrystal core; and at least one shelldisposed on the core, wherein at least one shell comprises ZnS andfluoride.

In some embodiments, the core comprises ZnSe, ZnSeTe, InP, or InAs.

In some embodiments, the core comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1.

In some embodiments, the nanostructure comprises two shells.

In some embodiments, at least one shell comprises a first shellcomprising ZnSe and a second shell comprising ZnS and fluoride. In someembodiments, at least one shell comprises a first shell comprising ZnSeand fluoride, and a second shell comprising ZnS and fluoride.

In some embodiments, the fluoride is in the form of a metal fluoride,ammonium fluoride, or tetraalkylammonium fluoride.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the fluoride is in the form of a metal fluorideselected from the group consisting of ZnF₂, HfF₄, and ZrF₄. In someembodiments, the metal fluoride is ZnF₂.

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising ZnSe or ZnSe_(1-x)Te_(x), wherein 0≤x<1,and a first metal fluoride; and at least one shell disposed on the core,wherein at least one shell comprises ZnS and optionally a second metalfluoride.

In some embodiments, the nanostructure comprises two shells.

In some embodiments, the first metal fluoride is selected from the groupconsisting of ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the second metal fluoride is selected from thegroup consisting of ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the nanostructure further comprises at least oneamine. In some embodiments, at least one amine is bound to the surfaceof the nanostructure.

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising a nanocrystal core; at least one shelldisposed on the core, wherein at least one shell comprises ZnS andfluoride; and at least one amine bound to the surface of thenanostructure.

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising a nanocrystal core; at least one shelldisposed on the core, wherein at last one shell comprises ZnS or ZnSe;at least one fluoride bound to the surface of the nanostructure; and atleast one amine bound to the surface of the nanostructure.

Nanostructure Film

In some embodiments, the present disclosure provides a nanostructurefilm comprising at least one population of nanostructures, thenanostructures comprising a core comprising a nanocrystal core; and atleast one shell disposed on the core, wherein at least one shellcomprises ZnS and fluoride.

In some embodiments, the present disclosure provides a nanostructurefilm comprising at least one population of nanostructures, thenanostructures comprising a core comprising a nanocrystal core; at leastone shell disposed on the core, wherein at least one shell comprises ZnSor ZnSe; at least one fluoride bound to the surface of thenanostructures; and at least one amine bound to the surface of thenanostructures.

In some embodiments, the present disclosure provides a nanostructurefilm comprising at least one population of nanostructures, thenanostructures comprising a core comprising ZnSe or ZnSe_(1-x)Te_(x),wherein 0≤x<1, and a first metal fluoride; and at least one shelldisposed on the core, wherein at least one shell comprises ZnS andoptionally a second metal fluoride.

In some embodiments, the present disclosure provides a nanostructurefilm comprising at least one population of nanostructures, thenanostructures comprising a core comprising InP; at least one shelldisposed on the core, wherein at least one shell comprises ZnS or ZnSe;at least one fluoride bound to the surface of the nanostructures; and atleast one amine bound to the surface of the nanostructures.

In some embodiments, the nanostructure film further comprises at leastone organic resin.

In some embodiments, the nanostructure is a quantum dot.

Nanostructure Molded Article

In some embodiments, the present disclosure provides a molded articlecomprising a nanostructure film described herein.

In some embodiments, the molded article comprises:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising a        nanocrystal core; and at least one shell disposed on the core,        wherein at least one shell comprises ZnS and fluoride.

In some embodiments, the molded article comprises:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising a        nanocrystal core; at least one shell disposed on the core,        wherein at least one shell comprises ZnS or ZnSe; at least one        fluoride bound to the surface of the nanostructures; and at        least one amine bound to the surface of the nanostructures.

In some embodiments, the molded article comprises:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising ZnSe        or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and a first metal fluoride;        and at least one shell disposed on the core, wherein at least        one shell comprises ZnS and optionally a second metal fluoride.

In some embodiments, the molded article comprises:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising InP;        at least one shell disposed on the core, wherein at least one        shell comprises ZnS or ZnSe; at least one fluoride bound to the        surface of the nanostructures; and at least one amine bound to        the surface of the nanostructures.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the molded article is an electroluminescent device.In some embodiments, the molded article is a light emitting diode. Insome embodiments, the molded article is a liquid crystal display.

Production of Nanostructures

Methods for colloidal synthesis of a variety of nanostructures are knownin the art. Such methods include techniques for controllingnanostructure growth, e.g., to control the size and/or shapedistribution of the resulting nanostructures.

In a typical colloidal synthesis, semiconductor nanostructures areproduced by rapidly injecting precursors that undergo pyrolysis into ahot solution (e.g., hot solvent and/or surfactant). The precursors canbe injected simultaneously or sequentially. The precursors rapidly reactto form nuclei. Nanostructure growth occurs through monomer addition tothe nuclei.

Surfactant molecules interact with the surface of the nanostructure. Atthe growth temperature, the surfactant molecules rapidly adsorb anddesorb from the nanostructure surface, permitting the addition and/orremoval of atoms from the nanostructure while suppressing aggregation ofthe growing nanostructures. In general, a surfactant that coordinatesweakly to the nanostructure surface permits rapid growth of thenanostructure, while a surfactant that binds more strongly to thenanostructure surface results in slower nanostructure growth. Thesurfactant can also interact with one (or more) of the precursors toslow nanostructure growth.

Nanostructure growth in the presence of a single surfactant typicallyresults in spherical nanostructures. Using a mixture of two or moresurfactants, however, permits growth to be controlled such thatnon-spherical nanostructures can be produced, if, for example, the two(or more) surfactants adsorb differently to different crystallographicfaces of the growing nanostructure.

A number of parameters are thus known to affect nanostructure growth andcan be manipulated, independently or in combination, to control the sizeand/or shape distribution of the resulting nanostructures. Theseinclude, e.g., temperature (nucleation and/or growth), precursorcomposition, time-dependent precursor concentration, ratio of theprecursors to each other, surfactant composition, number of surfactants,and ratio of surfactant(s) to each other and/or to the precursors.

Synthesis of Group II-VI nanostructures has been described, e.g., inU.S. Pat. Nos. 6,225,198, 6,322,901, 6,207,229, 6,607,829, 7,060,243,7,374,824, 6,861,155, 7,125,605, 7,566,476, 8,158,193, and 8,101,234 andU.S. Patent Appl. Publication Nos. 2011/0262752 and 2011/0263062, eachof which is incorporated herein by reference in their entireties.

Although Group II-VI nanostructures such as CdSe/CdS/ZnS core/shellnanostructures can exhibit desirable luminescence behavior, as notedabove, issues such as the toxicity of cadmium limit the applications forwhich such nanostructures can be used. Less toxic alternatives withfavorable luminescence properties are thus highly desirable.

In some embodiments, the nanostructures are free from cadmium. As usedherein, the term “free of cadmium” is intended that the nanostructurescontain less than 100 ppm by weight of cadmium. The Restriction ofHazardous Substances (RoHS) compliance definition requires that theremust be no more than 0.01% (100 ppm) by weight of cadmium in the rawhomogeneous precursor materials. The cadmium level in the Cd-freenanostructures of the present invention is limited by the trace metalconcentration in the precursor materials. The trace metal (includingcadmium) concentration in the precursor materials for the Cd-freenanostructures, is measured by inductively coupled plasma massspectroscopy (ICP-MS) analysis, and are on the parts per billion (ppb)level. In some embodiments, nanostructures that are “free of cadmium”contain less than about 50 ppm, less than about 20 ppm, less than about10 ppm, or less than about 1 ppm of cadmium.

In some embodiments, the nanostructure comprises a nanocrystal core. Insome embodiments, the core comprises ZnSe, ZnSeTe, InP, or InAs. In someembodiments, the core comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1. In someembodiments, the core comprises ZnSe. In some embodiments, the corecomprises InP.

In some embodiments, the nanostructure comprises at least one shelldisposed on the core. In some embodiments, at least one shell comprisesZnSe. In some embodiments, at least one shell comprises ZnS. In someembodiments, at least one shell comprises ZnSe and at least one shellcomprises ZnS.

In some embodiments, at least one shell comprises ZnS and fluoride. Insome embodiments, the nanostructure comprises two shells. In someembodiments, at least one shell comprises ZnSe. In some embodiments, atleast one shell comprises ZnSe and fluoride. In some embodiments, atleast one shell comprises a first shell comprising ZnSe and a secondshell comprising ZnS and fluoride. In some embodiments, the at least oneshell comprises a first shell comprising ZnSe and fluoride, and a secondshell comprising ZnS and fluoride. In some embodiments, the fluoride isin the form of a metal fluoride, ammonium fluoride, ortetraalkylammonium fluoride. In some embodiments, the fluoride is in theform of a metal fluoride selected from the group consisting of ZnF₂,HfF₄, and ZrF₄. In some embodiments, the metal fluoride is ZnF₂.

In some embodiments, the nanostructure comprises a core comprising InPand at least one shell comprising ZnS or ZnSe. In some embodiments, thenanostructure comprises a core comprising InP, at least one shellcomprising ZnS, and at least one shell comprising ZnSe.

In some embodiments, the nanostructure comprises a core comprising ZnSe,and at least one shell comprising ZnS and ZnF₂. In some embodiments, thenanostructure comprises a core comprising ZnSe, at least one shellcomprising ZnSe, and at least one shell comprising ZnS and ZnF₂. In someembodiments, the nanostructure comprises a core comprising ZnSe, atleast one shell comprising ZnSe and ZnF₂, and at least one shellcomprising ZnS and ZnF₂. In some embodiments, the nanostructurecomprises a core comprising ZnSe_(1-x)Te_(x), wherein 0≤x<1, and atleast one shell comprising ZnS and ZnF₂. In some embodiments, whereinthe nanostructure comprises a core comprising ZnSe_(1-x)Te_(x), wherein0≤x<1, at least one shell comprising ZnSe, and at least one shellcomprising ZnS and ZnF₂. In some embodiments, the nanostructurecomprises a core comprising ZnSe_(1-x)Te_(x), wherein 0≤x<1, at leastone shell comprising ZnSe and ZnF₂, and at least one shell comprisingZnS and ZnF₂.

In some embodiments, the nanostructure comprises a core comprising ZnSeor ZnSe_(1-x)Te_(x), wherein 0≤x<1, and a first metal fluoride. In someembodiments, the core comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1, and afirst metal fluoride. In some embodiments, the core comprises ZnSe and afirst metal fluoride. In some embodiments, the first metal fluoride isselected from the group consisting of ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the nanostructure comprises at least one shelldisposed on the core. In some embodiments, at least one shell comprisesZnS and optionally a second metal fluoride. In some embodiments, thenanostructure comprises two shells. In some embodiments, at least oneshell comprises ZnSe. In some embodiments, at least one shell comprisesa first shell comprising ZnSe and a second shell comprising ZnS andoptionally a second metal fluoride. In some embodiments, the secondmetal fluoride is selected from the group consisting of ZnF₂, HfF₄, andZrF₄.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride selected from the group consisting of ZnF₂, HfF₄,and ZrF₄; and at least one shell comprising ZnS and a metal fluorideselected from the group consisting of ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride selected from the group consisting of ZnF₂, HfF₄,and ZrF₄; at least one shell comprising ZnSe, and at least one shellcomprising ZnS and a metal fluoride selected from the group consistingof ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride selected from the group consisting of ZnF₂, HfF₄,and ZrF₄; and at least one shell comprising ZnS.

In some embodiments, the nanostructure comprises a core comprising ZnSeand a metal fluoride selected from the group consisting of ZnF₂, HfF₄,and ZrF₄; at least one shell comprising ZnSe; and at least one shellcomprising ZnS.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride selected from thegroup consisting of ZnF₂, HfF₄, and ZrF₄; and at least one shellcomprising ZnS and a metal fluoride selected from the group consistingof ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride selected from thegroup consisting of ZnF₂, HfF₄, and ZrF₄; at least one shell comprisingZnSe; and at least one shell comprising ZnS and a metal fluorideselected from the group consisting of ZnF₂, HfF₄, and ZrF₄.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride selected from thegroup consisting of ZnF₂, HfF₄, and ZrF₄; and at least one shellcomprising ZnS.

In some embodiments, the nanostructure comprises a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride selected from thegroup consisting of ZnF₂, HfF₄, and ZrF₄; at least one shell comprisingZnSe; and at least one shell comprising ZnS.

In some embodiments, the nanostructure is prepared using the method ofU.S. Application Publication No. 2017/0306227, which is incorporated byreference in its entirety.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the nanostructure is substantially cubic in shape.

Solvents

In some embodiments, the nanostructure further comprises a solvent.

In some embodiments, the solvent is selected from the group consistingof chloroform, acetone, hexane, heptane, octane, butanone, ethyleneglycol monoethyl ether, ethylene glycol monopropyl ether, 1,4-butanedioldiacetate, diethylene glycol monobutyl ether acetate, ethylene glycolmonobutyl ether acetate, glyceryl triacetate, heptyl acetate, hexylacetate, pentyl acetate, butyl acetate, ethyl acetate, diethylene glycolbutyl methyl ether, diethylene glycol monobutyl ether, di(proypleneglycol) dimethyl ether, diethylene glycol ethyl methyl ether, ethyleneglycol monobutyl ether, diethylene glycol diethyl ether, methyl ethylketone, methyl isobutyl ketone, monomethyl ether glycol ester,gamma-butyrolactone, methylacetic-3-ethyl ether, butyl carbitol, butylcarbitol acetate, propanediol monomethyl ether, propanediol monomethylether acetate, cyclohexane, toluene, xylene, isopropyl alcohol, andcombinations thereof.

In some embodiments, the solvent is a non-polar solvent. In someembodiments, the non-polar solvent is selected from the group consistingof hexane, heptane, octane, toluene, and mixtures thereof. In someembodiments, the non-polar solvent is octane. In some embodiments, thenon-polar solvent is hexane.

Production of Nanostructures with Fluoride Passivation in the Shell

In some embodiments, the present disclosure provides a method ofpreparing a nanostructure, comprising:

-   -   (a) providing a nanocrystal core;    -   (b) optionally admixing the core in (a) with a zinc source and a        selenium source to provide a core with a ZnSe shell;    -   (c) admixing the core in (a) or the core with a ZnSe shell        in (b) with a fluoride source; and    -   (d) infusing a solution comprising a zinc source and a sulfur        source into the admixture in (c);        to provide the nanostructure.

In some embodiments, the core comprises ZnSe, ZnSeTe, InP, or InAs. Insome embodiments, the core comprises ZnSe_(1-x)Te_(x), wherein 0≤x<1. Insome embodiments, the core comprises ZnSe.

In some embodiments, the molar ratio of the fluoride source to thenanocrystal core is between about 1:1 and about 30:1, about 1:1 andabout 25:1, about 1:1 and about 20:1, about 1:1 and about 15:1, about1:1 and about 10:1, about 1:1 and about 9:1, about 1:1 and about 8:1,about 1:1 and about 7:1, 1:1 and about 6:1, about 1:1 and about 5:1,about 1:1 and about 4:1, about 1:1 and about 3:1, or about 1:1 and about2:1. In some embodiments, the molar ratio of the fluoride source to thenanocrystal core is about 1:1, about 2:1, about 3:1, about 4:1, about5:1, about 6:1, about 7:1, about 8:1, about 9:1, about 10:1, about 11:1,about 12:1, about 13:1, about 14:1, about 15:1, about 16:1, about 17:1,about 18:1, about 19:1, about 20:1, about 21:1, about 22:1, about 23:1,about 24:1, about 25:1, about 26:1, about 27:1, about 28:1, about 29:1,or about 30:1.

In some embodiments, the zinc source in (b) is a dialkyl zinc compound.In some embodiments, the zinc source in (b) is a zinc carboxylate. Insome embodiments, the zinc source in (b) is diethylzinc, dimethylzinc,zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zincchloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate,zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate,zinc hexanoate, zinc octanoate, zinc laurate, zinc myristate, zincpalmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. Insome embodiments, the zinc source in (b) is zinc oleate, zinc hexanoate,zinc octanoate, zinc laurate, zinc myristate, zinc palmitate, zincstearate, zinc dithiocarbamate, or mixtures thereof. In someembodiments, the zinc source in (b) is zinc oleate.

In some embodiments, the selenium source in (b) is an alkyl-substitutedselenourea. In some embodiments, the selenium source in (b) is aphosphine selenide. In some embodiments, the selenium source in (b) isselected from trioctylphosphine selenide, tri(n-butyl)phosphineselenide, tri(sec-butyl)phosphine selenide, tri(tert-butyl)phosphineselenide, trimethylphosphine selenide, triphenylphosphine selenide,diphenylphosphine selenide, phenylphosphine selenide,tricyclohexylphosphine selenide, cyclohexylphosphine selenide,1-octaneselenol, 1-dodecaneselenol, selenophenol, elemental selenium,hydrogen selenide, bis(trimethylsilyl) selenide, selenourea, andmixtures thereof. In some embodiments, the selenium source in (b) istri(n-butyl)phosphine selenide, tri(sec-butyl)phosphine selenide, ortri(tert-butyl)phosphine selenide. In some embodiments, the seleniumsource in (b) is trioctylphosphine selenide.

In some embodiments, the admixing in (b) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the admixing in (b)is at a temperature of about 310° C.

In some embodiments, the admixing in (b) comprises admixing the core in(a) with a zinc source, a selenium source, and optionally a fluoridesource to provide a core with a shell comprising ZnSe and fluoride.

In some embodiments, the fluoride source is a metal fluoride, ammoniumfluoride, or tetraalkylammonium fluoride.

In some embodiments, the fluoride source is a metal fluoride selectedfrom the group consisting of ZnF₂, HfF₄, and ZrF₄. In some embodiments,the metal fluoride is ZnF₂. In some embodiments, the metal fluoride isHfF₄. In some embodiments, the metal fluoride is ZrF₄.

In some embodiments, the fluoride source is a tetraalkylammoniumfluoride selected from the group consisting of tetrabutylammoniumfluoride, tetrapropylammonium fluoride, diisopropyldimethylammoniumfluoride, tetraethylammonium fluoride, and tetramethylammonium fluoride,dioctadecyldimethylammonium fluoride, dihexadecyldimethylammoniumfluoride, ditetradecyldimethylammonium fluoride,didodecyldimethylammonium fluoride, didecyldimethylammonium fluoride,dioctyldimethylammonium fluoride, bis(ethylhexyl)dimethylammoniumfluoride, octadecyltrimethylammonium fluoride, oleyltrimethylammoniumfluoride, hexadecyltrimethylammonium fluoride,tetradecyltrimethylammonium fluoride, dodecyltrimethylammonium fluoride,decyltrimethylammonium fluoride, octyltrimethylammonium fluoride,phenylethyltrimethylammonium fluoride, benzyltrimethylammonium fluoride,phenyltrimethylammonium fluoride, benzylhexadecyldimethylammoniumfluoride, benzyltetradecyldimethylammonium fluoride,benzyldodecyldimethylammonium fluoride, benzyldecyldimethylammoniumfluoride, benzyloctyldimethylammonium fluoride, benzyltributylammoniumfluoride, and benzyltriethylammonium fluoride.

In some embodiments, the tetraalkylammonium fluoride istetrabutylammonium fluoride.

In some embodiments, the admixing in (c) is at a temperature betweenabout 20° C. and about 120° C. In some embodiments, the admixing in (c)is at a temperature of about 100° C.

In some embodiments, the admixing in (c) further comprises an aminesource.

In some embodiments, the amine source is a lower alkyl amine, an alkenylamine, a hydroalkyl amine, a haloalkyl amine, a primary aryl amine, asecondary aryl amine, or a heterocyclic amine. In some embodiments, theamine source is a secondary amine, i.e., amines having an amine groupcontaining two C—N bonds and one N—H bond. In some embodiments, theamine source contains a total of 20 carbon atoms or less. In someembodiments, the amine source contains 10 carbon atoms or less. Examplesof primary amines are alkylamines, such as ethylamine, butylamine,hexylamine, octylamine, decylamine, hexadecylamine, and octadecylamine;alkenylamines, such as allylamine, 2-hexenylamine, 4-decenylamine, andoctadecenyl amines; alkanolamines, such as ethanolamine, octanolamine,and dodecanolamine; haloalkylamines, such as betachloroethylamine; andarylamines, such as aniline. Examples of secondary amines which may beused to prepare the compounds described herein include dialkylamines,such as diethylamine, di-n-propylamine, diisobutylamine, dihexylamineand dioctylamine; dialkenylamines, such as diallylamine anddihexenylamine; dialkanolamines, such as diethanolamine anddidecanolamine; dihaloalkylamines, such as bis(beta-chloroethyl) amine;and N,N′-dialkylalkylenediamines, such as N,N-dimethylethylenediamine.The secondary amines do not necessarily have to contain two identicalsubstituents. Examples of such mixed amines includeN-methylethanolamine, N-methylallylamine and N-methylaniline. Additionalsecondary amines include those amines in which the amine nitrogen iscontained within a heterocyclic ring. In some embodiments, theheterocyclic amines are six-membered ring heterocyclic amines. Examplesof such heterocyclic amines include morpholine, piperidine, pyrrolidine,N-methylpiperazine, hexamethyleneimine, and thiomorpholine. In someembodiments, the heterocyclic amine may contain additional hetero atoms,for example, nitrogen, oxygen, or sulfur.

In some embodiments, the zinc source in (d) is a dialkyl zinc compound.In some embodiments, the zinc source in (d) is a zinc carboxylate. Insome embodiments, the zinc source in (d) is diethylzinc, dimethylzinc,zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zincchloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate,zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate,zinc hexanoate, zinc octanoate, zinc laurate, zinc myristate, zincpalmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. Insome embodiments, the zinc source in (d) is zinc oleate, zinc hexanoate,zinc octanoate, zinc laurate, zinc myristate, zinc palmitate, zincstearate, zinc dithiocarbamate, or mixtures thereof. In someembodiments, the zinc source in (d) is zinc oleate.

In some embodiments, the sulfur source in (d) is selected from the groupconsisting of trioctylphosphine sulfide, elemental sulfur, octanethiol,dodecanethiol, octadecanethiol, tributylphosphine sulfide, cyclohexylisothiocyanate, α-toluenethiol, ethylene trithiocarbonate, allylmercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, andcombinations thereof. In some embodiments, the sulfur source in (d) istrioctylphosphine sulfide.

In some embodiments, the infusing in (d) is at a temperature betweenabout 280° C. and about 320° C. In some embodiments, the infusing in (d)is at a temperature of about 310° C.

In some embodiments, the infusing in (d) is at an infusing rate betweenabout 0.05 mL/min and about 5.0 mL/min. In some embodiments, theinfusing in (d) is at an infusing rate of about 0.1 mL/min.

In some embodiments, the molar ratio of fluoride bound to thenanostructure to zinc in the nanostructure is between about 0.05 andabout 0.35. In some embodiments, the molar ratio of fluoride bound tothe nanostructure to zinc in the nanostructure is about 0.13.

In some embodiments, the nanostructure is cooled to room temperature. Insome embodiments, an organic solvent is added to dilute the reactionmixture comprising the nanostructure.

In some embodiments, the organic solvent used to dilute the reactionmixture is ethanol, hexane, pentane, toluene, benzene, diethylether,acetone, ethyl acetate, dichloromethane (methylene chloride),chloroform, dimethylformamide, or N-methylpyrrolidinone. In someembodiments, the organic solvent is toluene. In some embodiments, theorganic solvent is a combination of toluene and ethanol.

In some embodiments, the nanostructures are isolated. In someembodiments, the nanostructure is isolated by precipitation using anorganic solvent. In some embodiments, the nanostructure is isolated byflocculation with ethanol. In some embodiments, the nanostructures arefurther isolated by centrifugation followed by decanting of the organicsolvent.

Production of Nanostructures with Fluoride Passivation in the Core

In some embodiments, the present disclosure provides a method ofpreparing a nanostructure, comprising:

-   -   (a) admixing a solution of a zinc source, a selenium source, and        a first metal fluoride source to provide a core comprising ZnSe        or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and the first metal        fluoride;    -   (b) optionally admixing the core in (a) with a zinc source and a        selenium source to provide a core with a ZnSe shell;    -   (c) optionally admixing the core in (a) or the core with a ZnSe        shell in (b) with a second metal fluoride source; and    -   (d) infusing a solution comprising a zinc source and a sulfur        source into the admixture in (a), (b), or (c);        to provide a nanostructure.

In some embodiments, the molar ratio of the first metal fluoride sourceto the core is between about 1:1 and 10:1, about 1:1 and about 9:1,about 1:1 and 8:1, about 1:1 and about 7:1, about 1:1 and about 6:1,about 1:1 and about 5:1, about 1:1 and about 4:1, about 1:1 and about3:1, or about 1:1 and about 2:1. In some embodiments, the molar ratio ofthe first metal fluoride source to the core is about 1:1, about 2:1,about 3:1, about 4:1, about 5:1, about 6:1, about 7:1, about 8:1, about9:1, or about 10:1.

In some embodiments, the molar ratio of the second metal fluoride sourceto the core is between about 1:1 and about 30:1, about 1:1 and about25:1, about 1:1 and about 20:1, about 1:1 and about 15:1, about 1:1 andabout 10:1, about 1:1 and about 9:1, about 1:1 and about 8:1, about 1:1and about 7:1, 1:1 and about 6:1, about 1:1 and about 5:1, about 1:1 andabout 4:1, about 1:1 and about 3:1, or about 1:1 and about 2:1. In someembodiments, the molar ratio of the second fluoride source to thenanocrystal core is about 1:1, about 2:1, about 3:1, about 4:1, about5:1, about 6:1, about 7:1, about 8:1, about 9:1, about 10:1, about 11:1,about 12:1, about 13:1, about 14:1, about 15:1, about 16:1, about 17:1,about 18:1, about 19:1, about 20:1, about 21:1, about 22:1, about 23:1,about 24:1, about 25:1, about 26:1, about 27:1, about 28:1, about 29:1,or about 30:1.

In some embodiments, the selenium source in (a) is selected from thegroup consisting of trioctylphosphine selenide, tri(n-butyl)phosphineselenide, tri(sec-butyl)phosphine selenide, tri(tert-butyl)phosphineselenide, trimethylphosphine selenide, triphenylphosphine selenide,diphenylphosphine selenide, phenylphosphine selenide,cyclohexylphosphine selenide, octaselenol, dodecaselenol, selenophenol,elemental selenium, hydrogen selenide, bis(trimethylsilyl) selenide, andmixtures thereof. In some embodiments, the selenium source in (a) istrioctylphosphine selenide.

In some embodiments, the zinc source in (a) is a dialkyl zinc compound.In some embodiments, the zinc source in (a) is a zinc carboxylate. Insome embodiments, the zinc source in (a) is diethylzinc, dimethylzinc,zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zincchloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate,zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate,zinc hexanoate, zinc octanoate, zinc laurate, zinc myristate, zincpalmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. Insome embodiments, the zinc source in (a) is zinc oleate, zinc hexanoate,zinc octanoate, zinc laurate, zinc myristate, zinc palmitate, zincstearate, zinc dithiocarbamate, or mixtures thereof. In someembodiments, the zinc source in (a) is zinc oleate.

In some embodiments, the first metal fluoride in (a) is selected fromthe group consisting of ZnF₂, HfF₄, and ZrF₄. In some embodiments, thefirst metal fluoride source in (a) is ZnF₂. In some embodiments, thefirst metal fluoride source in (a) is HfF₄. In some embodiments, thefirst metal fluoride source in (a) is ZrF₄.

In some embodiments, the admixing in (a) further comprises a first aminesource.

In some embodiments, the amine source is a lower alkyl amine, an alkenylamine, a hydroalkyl amine, a haloalkyl amine, a primary aryl amine, asecondary aryl amine, or a heterocyclic amine. In some embodiments, theamine source is a secondary amine, i.e., amines having an amine groupcontaining two C—N bonds and one N—H bond. In some embodiments, theamine source contains a total of 20 carbon atoms or less. In someembodiments, the amine source contains 10 carbon atoms or less. Examplesof primary amines are alkylamines, such as ethylamine, butylamine,hexylamine, octylamine, decylamine, hexadecylamine, and octadecylamine;alkenylamines, such as allylamine, 2-hexenylamine, 4-decenylamine, andoctadecenyl amines; alkanolamines, such as ethanolamine, octanolamine,and dodecanolamine; haloalkylamines, such as betachloroethylamine; andarylamines, such as aniline. Examples of secondary amines which may beused to prepare the compounds described herein include dialkylamines,such as diethylamine, di-n-propylamine, diisobutylamine, dihexylamineand dioctylamine; dialkenylamines, such as diallylamine anddihexenylamine; dialkanolamines, such as diethanolamine anddidecanolamine; dihaloalkylamines, such as bis(beta-chloroethyl) amine;and N,N′-dialkylalkylenediamines, such as N,N-dimethylethylenediamine.The secondary amines do not necessarily have to contain two identicalsubstituents. Examples of such mixed amines includeN-methylethanolamine, N-methylallylamine and N-methylaniline. Additionalsecondary amines include those amines in which the amine nitrogen iscontained within a heterocyclic ring. In some embodiments, theheterocyclic amines are six-membered ring heterocyclic amines. Examplesof such heterocyclic amines include morpholine, piperidine, pyrrolidine,N-methylpiperazine, hexamethyleneimine, and thiomorpholine. In someembodiments, the heterocyclic amine may contain additional hetero atoms,for example, nitrogen, oxygen, or sulfur.

In some embodiments, the admixing in (a) is at a temperature betweenabout 70° C. and about 130° C. In some embodiments, the admixing in (a)is at a temperature of about 100° C.

In some embodiments, the zinc source in (b) is a dialkyl zinc compound.In some embodiments, the zinc source in (b) is a zinc carboxylate. Insome embodiments, the zinc source in (b) is diethylzinc, dimethylzinc,zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zincchloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate,zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate,zinc hexanoate, zinc octanoate, zinc laurate, zinc myristate, zincpalmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. Insome embodiments, the zinc source in (b) is zinc oleate, zinc hexanoate,zinc octanoate, zinc laurate, zinc myristate, zinc palmitate, zincstearate, zinc dithiocarbamate, or mixtures thereof. In someembodiments, the zinc source in (b) is zinc oleate.

In some embodiments, the selenium source in (b) is selected from thegroup consisting of trioctylphosphine selenide, tri(n-butyl)phosphineselenide, tri(sec-butyl)phosphine selenide, tri(tert-butyl)phosphineselenide, trimethylphosphine selenide, triphenylphosphine selenide,diphenylphosphine selenide, phenylphosphine selenide,cyclohexylphosphine selenide, octaselenol, dodecaselenol, selenophenol,elemental selenium, hydrogen selenide, bis(trimethylsilyl) selenide, andmixtures thereof. In some embodiments, the selenium source in (b) istrioctylphosphine selenide.

In some embodiments, the admixing in (b) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the admixing in (b)is at a temperature of about 310° C.

In some embodiments, the second metal fluoride source in (c) is selectedfrom the group consisting of ZnF₂, HfF₄, and ZrF₄. In some embodiments,the second metal fluoride source in (c) is ZnF₂. In some embodiments,the second metal fluoride source (c) is HfF₄. In some embodiments, thesecond metal fluoride source (c) is ZrF₄.

In some embodiments, the admixing in (c) further comprises a secondamine source.

In some embodiments, the amine source is a lower alkyl amine, an alkenylamine, a hydroalkyl amine, a haloalkyl amine, a primary aryl amine, asecondary aryl amine, or a heterocyclic amine. In some embodiments, theamine source is a secondary amine, i.e., amines having an amine groupcontaining two C—N bonds and one N—H bond. In some embodiments, theamine source contains a total of 20 carbon atoms or less. In someembodiments, the amine source contains 10 carbon atoms or less. Examplesof primary amines are alkylamines, such as ethylamine, butylamine,hexylamine, octylamine, decylamine, hexadecylamine, and octadecylamine;alkenylamines, such as allylamine, 2-hexenylamine, 4-decenylamine, andoctadecenyl amines; alkanolamines, such as ethanolamine, octanolamine,and dodecanolamine; haloalkylamines, such as betachloroethylamine; andarylamines, such as aniline. Examples of secondary amines which may beused to prepare the compounds described herein include dialkylamines,such as diethylamine, di-n-propylamine, diisobutylamine, dihexylamineand dioctylamine; dialkenylamines, such as diallylamine anddihexenylamine; dialkanolamines, such as diethanolamine anddidecanolamine; dihaloalkylamines, such as bis(beta-chloroethyl) amine;and N,N′-dialkylalkylenediamines, such as N,N-dimethylethylenediamine.The secondary amines do not necessarily have to contain two identicalsubstituents. Examples of such mixed amines includeN-methylethanolamine, N-methylallylamine and N-methylaniline. Additionalsecondary amines include those amines in which the amine nitrogen iscontained within a heterocyclic ring. In some embodiments, theheterocyclic amines are six-membered ring heterocyclic amines. Examplesof such heterocyclic amines include morpholine, piperidine, pyrrolidine,N-methylpiperazine, hexamethyleneimine, and thiomorpholine. In someembodiments, the heterocyclic amine may contain additional hetero atoms,for example, nitrogen, oxygen, or sulfur.

In some embodiments, the admixing in (c) is at a temperature betweenabout 70° C. and about 130° C. In some embodiments, the admixing in (c)is at a temperature of about 100° C.

In some embodiments, the zinc source in (d) is a dialkyl zinc compound.In some embodiments, the zinc source in (d) is a zinc carboxylate. Insome embodiments, the zinc source in (d) is diethylzinc, dimethylzinc,zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zincchloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate,zinc oleate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate,zinc hexanoate, zinc octanoate, zinc laurate, zinc myristate, zincpalmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. Insome embodiments, the zinc source in (d) is zinc oleate, zinc hexanoate,zinc octanoate, zinc laurate, zinc myristate, zinc palmitate, zincstearate, zinc dithiocarbamate, or mixtures thereof. In someembodiments, the zinc source in (d) is zinc oleate.

In some embodiments, the sulfur source in (d) is selected from the groupconsisting of trioctylphosphine sulfide, elemental sulfur, octanethiol,dodecanethiol, octadecanethiol, tributylphosphine sulfide, cyclohexylisothiocyanate, α-toluenethiol, ethylene trithiocarbonate, allylmercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, andcombinations thereof. In some embodiments, the sulfur source in (d) istrioctylphosphine sulfide.

In some embodiments, the infusing in (d) is at a temperature betweenabout 250° C. and about 350° C. In some embodiments, the infusing in (d)is at a temperature of about 310° C.

In some embodiments, the infusing in (d) is at an infusing rate betweenabout 0.05 mL/min and about 5.0 mL/min. In some embodiments, theinfusing in (d) is at an infusing rate of about 0.5 mL/min.

In some embodiments, the molar ratio of fluoride bound to thenanostructure to zinc in the nanostructure is between about 0.05 andabout 0.35.

In some embodiments, the nanostructure is cooled to room temperature. Insome embodiments, an organic solvent is added to dilute the reactionmixture comprising the nanostructure.

In some embodiments, the organic solvent used to dilute the reactionmixture is ethanol, hexane, pentane, toluene, benzene, diethylether,acetone, ethyl acetate, dichloromethane (methylene chloride),chloroform, dimethylformamide, or N-methylpyrrolidinone. In someembodiments, the organic solvent is toluene. In some embodiments, theorganic solvent is a combination of toluene and ethanol.

In some embodiments, the nanostructure is isolated. In some embodiments,the nanostructure is isolated by precipitation using an organic solvent.In some embodiments, the nanostructure is isolated by flocculation withethanol. In some embodiments, the nanostructures are further isolated bycentrifugation followed by decanting of the organic solvent.

Amine Passivation

In some embodiments, the present disclosure provides a nanostructurecomprising a core comprising a nanocrystal core; at least one shelldisposed on the core, wherein at least one shell comprises ZnS andfluoride; and at least one amine bound to the nanostructure. In someembodiments, the present disclosure provides a nanostructure comprisinga core comprising a nanocrystal core; at least one shell disposed on thecore, wherein at least one shell comprises ZnS; at least one fluoridebound to the nanostructure; and at least one amine bound to thenanostructure.

The native ligand set (e.g., carboxylates and phosphines) of mostquantum dots are not soluble in a wide range of organic media and areincompatible with matrix materials commonly used in the preparation ofquantum dots films. Ligand exchange can be used to solve these problemsbut the exchange may influence surface trap states and hence, thephotoluminescence quantum yield of the quantum dots. And, it has foundthat photoluminescence quantum yield and ligation are not simplyrelated, not only because of their nonlinear independence, but alsobecause metal carboxylates complexes can concurrently be displaced withamine binding.

Furthermore, quantum dots, especially InP quantum dots, are known to besensitive to primary amines. This sensitivity limits the choice ofmatrix materials and/or ligands that can be used with InP quantum dots.

Attempts to lower the relative extent of quenching of InP quantum dotshave shown only moderate success. For example, it was found that the useof a thick inorganic shell coating on InP quantum dots can lower theextent of quantum yield quenching by amines. As shown in FIG. 11, thethickest shell coating comprising 2.5 monolayers of ZnSe and 6.5monolayers of ZnS prevented a greater amount of quantum dot quenching bydodecylamine than the thinnest shell coating comprising 2.5 monolayersof ZnSe and 2.5 monolayers of ZnS. However, quantum dots with very thickshells may suffer from strain-induced interface traps which mayultimately cause a lower absolute quantum yield.

Studies on the coordination chemistry of carboxylate-terminated CdSe,CdS, PbSe, and PbS quantum dots provide an explanation of the quenchingmechanism (Anderson, N.C., et al., J. Am. Chem. Soc. 135:18536-18548(2013)). As shown in FIG. 12, a neutral Lewis base ligand (L), such asan amine, readily displace a metal carboxylate (MX₂, wherein M is Cd orPb; and X is O₂CR, Cl, or SR) from carboxylate-terminated CdSe, CdS,PbS, or PbS quantum dots. Amine molecules coordinate to the metalcarboxylate and to metal sites on the quantum dot surfaces. Theresultant amine-metal complex is highly soluble and thus, is easilyremoved from the quantum dot surface.

Amines can bind to the surface of metal sites. Model studies have shownthat amines prevent reduction of Cd²⁺ to Cd—Cd dimers on negativelycharged CdTe quantum dots (du Fosse, I., et al., Chem. Mater.31:4575-4583 (2019)). For example, it is believed that the binding ofamines to the surface of quantum dots comprising fluoride ligands isfacilitated by the low space demand of a fluoride ligand, such as zincfluoride, compared to a native ligand, such as zinc oleate. Therefore,fluoride ligands and amines can coexist on the quantum dot surface andpassivate both hole and electron traps.

In some embodiments, the amine bound to the surface of the nanostructureis a lower alkyl amine, an alkenyl amine, a hydroalkyl amine, ahaloalkyl amine, a primary aryl amine, a secondary aryl amine, or aheterocyclic amine. In some embodiments, the amine bound to the surfaceof the nanostructure is a secondary amine, i.e., amines having an aminegroup containing two C—N bonds and one N—H bond. In some embodiments,the amine bound to the surface of the nanostructure contains a total of20 carbon atoms or less. In some embodiments, the amine bound to thesurface of the nanostructure contains 10 carbon atoms or less. Examplesof primary amines are alkylamines, such as ethylamine, butylamine,hexylamine, octylamine, decylamine, hexadecylamine, and octadecylamine;alkenylamines, such as allylamine, 2-hexenylamine, 4-decenylamine, andoctadecenyl amines; alkanolamines, such as ethanolamine, octanolamine,and dodecanolamine; haloalkylamines, such as betachloroethylamine; andarylamines, such as aniline. Examples of secondary amines which can bindto the surface of the nanostructures described herein includedialkylamines, such as diethylamine, di-n-propylamine, diisobutylamine,dihexylamine and dioctylamine; dialkenylamines, such as diallylamine anddihexenylamine; dialkanolamines, such as diethanolamine anddidecanolamine; dihaloalkylamines, such as bis(beta-chloroethyl) amine;and N,N′-dialkylalkylenediamines, such as N,N-dimethylethylenediamine.The secondary amines do not necessarily have to contain two identicalsubstituents. Examples of such mixed amines includeN-methylethanolamine, N-methylallylamine and N-methylaniline. Additionalsecondary amines include those amines in which the amine nitrogen iscontained within a heterocyclic ring. In some embodiments, theheterocyclic amines are six-membered ring heterocyclic amines. Examplesof such heterocyclic amines include morpholine, piperidine, pyrrolidine,N-methylpiperazine, hexamethyleneimine, and thiomorpholine. In someembodiments, the heterocyclic amine may contain additional hetero atoms,for example, nitrogen, oxygen, or sulfur.

First Ligands

In some embodiments, the nanostructures comprise ligands bound to theirsurface. In some embodiments, the nanostructures include a coating layercomprising ligands to protect the nanostructures from external moistureand oxidation, to control aggregation, and to allow for dispersion ofthe nanostructures in the matrix material. Suitable first ligandsinclude those disclosed in U.S. Pat. Nos. 6,949,206; 7,267,875;7,374,807; 7,572,393; 7,645,397; and 8,563,133 and in U.S. Patent Appl.Publication Nos. 2008/0237540; 2008/0281010; and 2010/0110728, which areincorporated herein by reference in their entireties.

In some embodiments, the nanostructure comprises a multi-part ligandstructure, such as the three-part ligand structure disclosed in U.S.Patent Appl. Publication No. 2008/237540, in which the head-group,tail-group, and middle/body group are independently fabricated andoptimized for their particular function, and then combined into anideally functioning complete surface ligand.

In some embodiments, the first ligands comprise one or more organicpolymeric ligands. Suitable ligands provide: efficient and strongbonding quantum dot encapsulation with low oxygen permeability;precipitate or segregate into domain in the matrix material to form adiscontinuous dual-phase or multi-phase matrix; disperse favorablythroughout the matrix material; and are commercially available materialsor can be easily formulated from commercially available materials.

In some embodiments, the first ligand comprises a carboxy, a thiol, aphosphine, or a phosphine oxide group.

In some embodiments, the first ligand comprises a carboxy group. In someembodiments, the first ligand comprises a carboxylic acid group. In someembodiments, the first ligand comprises a carboxylic acid group and thecarboxylic acid is a caprylic acid, capric acid, lauric acid, myristicacid, or palmitic acid. In some embodiments, the first ligand is acarboxylate. In some embodiments, the first ligand comprises acarboxylate and the carboxylate is a carboxyalkyl.

In some embodiments, the first ligand comprises a metal carboxylate. Insome embodiments, the first ligand is a metal carboxylate selected fromthe group consisting of zinc oleate, zinc hexanoate, zinc laurate, zincmyristate, zinc palmitate, zinc stearate, and zinc PEG-carboxylate. Insome embodiments, the first ligand is a metal carboxylate selected fromthe group consisting of zinc oleate, zinc laurate, and zincPEG-carboxylate. In some embodiments, the first ligand is zinc oleate.

In some embodiments, the first ligand comprises a phosphine group. Insome embodiments, the first ligand comprises a phosphine group and thephosphine group is triphenylphosphine, tributylphosphine,trihexylphosphine, trioctylphosphine (TOP), or tridecylphosphine.

In some embodiments, the first ligand comprises a phosphine oxide group.In some embodiments, the first ligand comprises a phosphine oxide groupand the phosphine oxide is triphenylphosphine oxide, tributylphosphineoxide, trihexylphosphine oxide, trioctylphosphine oxide (TOPO), ortridecylphosphine oxide.

Ligand Exchange

In some embodiments, the present invention is directed to a method forexchanging ligands on nanostructures. In some embodiments, a firstligand on a nanostructure is exchanged with at least one fluorideligand. During the ligand exchange, at least one functional group of thefluoride ligand displaces the native hydrophobic ligands of thenanostructure and affords a stable anchoring of the ligand onto thenanocrystal surface. In some embodiments, the nanostructure is a quantumdot.

In some embodiments, the first ligand is bound covalently to thenanostructure. In some embodiments, the first ligand is boundnon-covalently to the nanostructure.

In some embodiments, the present disclosure is directed to a method ofreplacing a first ligand on a nanostructure with a second ligandcomprising:

-   -   admixing a reaction mixture comprising a population of        nanostructures having the first ligand bound to the        nanostructure and at least one fluoride ligand which is the        second ligand, such that the second ligand displaces the first        ligand and becomes bound to the nanostructure.

In some embodiments, the fluoride ligand is selected from a metalfluoride, an ammonium fluoride, or a tetraalkylammonium fluoride.

In some embodiments, the fluoride ligand is a metal fluoride selectedfrom the group consisting of ZnF₂, HfF₄, and ZrF₄. In some embodiments,the metal fluoride is ZnF₂. In some embodiments, the metal fluoride isHfF₄. In some embodiments, the metal fluoride is ZrF₄.

In some embodiments, the fluoride ligand is a tetraalkylammoniumfluoride selected from the group consisting of tetrabutylammoniumfluoride, tetrapropylammonium fluoride, diisopropyldimethylammoniumfluoride, tetraethylammonium fluoride, and tetramethylammonium fluoride,dioctadecyldimethylammonium fluoride, dihexadecyldimethylammoniumfluoride, ditetradecyldimethylammonium fluoride,didodecyldimethylammonium fluoride, didecyldimethylammonium fluoride,dioctyldimethylammonium fluoride, bis(ethylhexyl)dimethylammoniumfluoride, octadecyltrimethylammonium fluoride, oleyltrimethylammoniumfluoride, hexadecyltrimethylammonium fluoride,tetradecyltrimethylammonium fluoride, dodecyltrimethylammonium fluoride,decyltrimethylammonium fluoride, octyltrimethylammonium fluoride,phenylethyltrimethylammonium fluoride, benzyltrimethylammonium fluoride,phenyltrimethylammonium fluoride, benzylhexadecyldimethylammoniumfluoride, benzyltetradecyldimethylammonium fluoride,benzyldodecyldimethylammonium fluoride, benzyldecyldimethylammoniumfluoride, benzyloctyldimethylammonium fluoride, benzyltributylammoniumfluoride, and benzyltriethylammonium fluoride.

In some embodiments, the tetraalkylammonium fluoride istetrabutylammonium fluoride.

In some embodiments, the fluoride ligand is tetrabutylammonium fluoride.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the second ligand becomes covalently bound to thenanostructure. In some embodiments, the second ligand becomesnon-covalently bound to the nanostructure.

In some embodiments, the admixing is performed at a temperature betweenabout 0° C. and about 200° C., about 0° C., and about 150° C., about 0°C. and about 100° C., about 0° C. and about 80° C., about 20° C. andabout 200° C., about 20° C. and about 150° C., about 20° C. and about100° C., about 20° C. and about 80° C., about 50° C. and about 200° C.,about 50° C. and about 150° C., about 50° C. and about 100° C., about50° C. and about 80° C., about 80° C. and about 200° C., about 80° C.and about 150° C., about 80° C. and about 1.00° C., about 100° C. andabout 200° C., about 100° C. and about 150° C., or about 150° C. andabout 200° C. In some embodiments, the admixing is performed at atemperature between about 50 T and about 100° C. In some embodiments,the admixing is performed at a temperature of about 70° C.

In some embodiments, the admixing is performed over a period of about 1minute and about 6 hours, about 1 minute and about 2 hours, about 1minute and about 1 hour, about 1 minute and about 40 minutes, about 1minute and about 30 minutes, about 1 minute and about 20 minutes, about1 minute and about 10 minutes, about 10 minutes and about 6 hours, about10 minutes and about 2 hours, about 10 minutes and about 1 hour, about10 minutes and about 40 minutes, about 10 minutes and about 30 minutes,about 10 minutes and about 20 minutes, about 20 minutes and about 6hours, about 20 minutes and about 2 hours, about 20 minutes and about 1hour, about 20 minutes and about 40 minutes, about 20 minutes and about30 minutes, about 30 minutes and about 6 hours, about 30 minutes andabout 2 hours, about 30 minutes and about 1 hour, about 30 minutes andabout 40 minutes, about 40 minutes and about 6 hours, about 40 minutesand about 2 hours, about 40 minutes and about 1 hour, about 1 hour andabout 6 hours, about 1 hour and about 2 hours, or about 2 hours andabout 6 hours. In some embodiments, the admixing is performed over aperiod of about 40 minutes and about 2 hours. In some embodiments, theadmixing is performed over a period of about 1 hour.

In some embodiments, the reaction mixture further comprises a solvent.In some embodiments, the solvent is selected from the group consistingof chloroform, acetone, butanone, tetrahydrofuran,2-methyltetrahydrofuran, ethylene glycol monoethyl ether, ethyleneglycol monopropyl ether, ethylene glycol monobutyl ether, di ethyleneglycol diethyl ether, methyl isobutyl ketone, monomethyl ether glycolester, gamma-butyrolactone, methylacetic-3-ethyl ether, butyl carbitol,butyl carbitol acetate, propanediol monomethyl ether, propanediolmonomethyl ether acetate; cyclohexane, toluene, xylene, isopropylalcohol, and combinations thereof. In some embodiments, the solvent istoluene.

The percentage of first ligands displaced by fluoride ligands can bemeasured by ¹⁹F NMR or Fourier-transform infrared spectroscopy (FTIR).In some embodiments, the mole percentage of first ligands displaced bythe fluoride ligands is between about 20% and about 100%, about 20% andabout 80%, about 20% and about 60%, about 20% and about 40%, about 25%and about 100%, about 25% and about 80%, about 25% and about 60%, about25% and about 40%, about 30% and about 100%, about 30% and about 80%,about 30% and about 60%, about 30% and about 40%, about 40% and about100%, about 40% and about 80%, about 40% and about 60%, about 60% andabout 100%, about 60% and about 80%, or about 80% and about 100%.

The percentage of fluoride ligands that are bound to a nanostructure ina population of nanostructures can be measured by ¹⁹F NMR, wherein thebound ligands are calculated using: (bound fluoride ligands)/(bound+freefluoride ligands).

In some embodiments, the mole percentage of fluoride ligands bound to ananostructures is between about 20% and about 100% is between about 20%and about 100%, about 20% and about 80%, about 20% and about 60%, about20% and about 40%, about 25% and about 100%, about 25% and about 80%,about 25% and about 60%, about 25% and about 40%, about 30% and about100%, about 30% and about 80%, about 30% and about 60%, about 30% andabout 40%, about 40% and about 100%, about 40% and about 80%, about 40%and about 60%, about 60% and about 100%, about 60% and about 80%, orabout 80% and about 100%.

Production of Nanostructures with Fluoride Ligands and Amines

In some embodiments, the present disclosure provides a method ofpreparing a nanostructure, comprising admixing:

-   -   (a) a nanostructure comprising a nanocrystal core and at least        one shell disposed on the core, wherein at least one shell        comprises ZnS or ZnSe; and    -   (b) at least one fluoride source; and    -   (c) at least one amine source;        to provide a nanostructure.

In some embodiments, the molar ratio of the fluoride source to thenanostructure is between about 0.5:1 and about 10:1, about 0.5:1 andabout 9:1, about 0.5:1 and 8:1, about 0.5:1 and about 7:1, about 0.5:1and about 6:1, about 0.5:1 and about 5:1, about 0.5:1 and about 4:1,about 0.5:1 and about 3:1, about 0.5:1 and about 2:1, or about 0.5:1 andabout 1:1. In some embodiments, the molar ratio of the fluoride sourceto the nanostructure is about 0.5:1, about 1:1, about 2:1, about 3:1,about 4:1, about 5:1, about 6:1, about 7:1, about 8:1, about 9:1, orabout 10:1.

In some embodiments, the nanostructure in (a) is InP/ZnSe/ZnS. In someembodiments, the nanostructure in (a) is red-emitting InP/ZnSe/ZnS. Insome embodiments, the nanostructure in (a) is green-emittingInP/ZnSe/ZnS.

In some embodiments, the fluoride source in (b) is selected from thegroup consisting of tetraalkylammonium fluoride, ZnF₂, HfF₄, and ZrF₄.In some embodiments, the fluoride source in (b) is ZnF₂. In someembodiments, the fluoride source in (b) is HfF₄. In some embodiments,the fluoride source in (b) is ZrF₄. In some embodiments, the fluoridesource in (b) is a tetraalkylammonium fluoride.

In some embodiments, the amine source in (c) is a lower alkyl amine, analkenyl amine, a hydroalkyl amine, a haloalkyl amine, a primary arylamine, a secondary aryl amine, or a heterocyclic amine. In someembodiments, the amine source in (c) is a secondary amine, i.e., amineshaving an amine group containing two C—N bonds and one N—H bond. In someembodiments, the amine source in (c) contains a total of 20 carbon atomsor less. In some embodiments, the amine source in (c) contains 10 carbonatoms or less. Examples of primary amines are alkylamines, such asethylamine, butylamine, hexylamine, octylamine, decylamine,hexadecylamine, and octadecylamine; alkenylamines, such as allylamine,2-hexenylamine, 4-decenylamine, and octadecenyl amines; alkanolamines,such as ethanolamine, octanolamine, and dodecanolamine; haloalkylamines,such as betachloroethylamine; and arylamines, such as aniline. Examplesof secondary amines which may be used to prepare the compounds describedherein include dialkylamines, such as diethylamine, di-n-propylamine,diisobutylamine, dihexylamine and dioctylamine; dialkenylamines, such asdiallylamine and dihexenylamine; dialkanolamines, such as diethanolamineand didecanolamine; dihaloalkylamines, such as bis(beta-chloroethyl)amine; and N,N′-dialkylalkylenediamines, such asN,N-dimethylethylenediamine. The secondary amines do not necessarilyhave to contain two identical substituents. Examples of such mixedamines include N-methylethanolamine, N-methylallylamine andN-methylaniline. Additional secondary amines include those amines inwhich the amine nitrogen is contained within a heterocyclic ring. Insome embodiments, the heterocyclic amines are six-membered ringheterocyclic amines. Examples of such heterocyclic amines includemorpholine, piperidine, pyrrolidine, N-methylpiperazine,hexamethyleneimine, and thiomorpholine. In some embodiments, theheterocyclic amine may contain additional hetero atoms, for example,nitrogen, oxygen, or sulfur. In some embodiments, the amine source isoctylamine.

In some embodiments, the admixing is at a temperature between about 50°C. and about 130° C. In some embodiments, the admixing is at atemperature between about 50° C. and about 130°, about 50° C. and about100° C., about 50° C. and about 70° C., about 70° C. and about 130° C.,about 70° C. and about 100° C., or about 100° C. and about 130° C. Insome embodiments, the admixing is at a temperature of about 70° C.

In some embodiments, the molar ratio of fluoride bound to thenanostructure is between about 0.05 and about 0.35.

In some embodiments, the nanostructure is cooled to room temperature. Insome embodiments, an organic solvent is added to dilute the reactionmixture comprising the nanostructure.

In some embodiments, the organic solvent used to dilute the reactionmixture is ethanol, hexane, pentane, toluene, benzene, diethylether,acetone, ethyl acetate, dichloromethane (methylene chloride),chloroform, dimethylformamide, or N-methylpyrrolidinone. In someembodiments, the organic solvent is toluene. In some embodiments, theorganic solvent is a combination of toluene and ethanol.

In some embodiments, the nanostructure is isolated. In some embodiments,the nanostructure is isolated by precipitation using an organic solvent.In some embodiments, the nanostructure is isolated by flocculation withethanol. In some embodiments, the nanostructures are further isolated bycentrifugation followed by decanting of the organic solvent.

Improved Properties of Nanostructures

In some embodiments, the core/shell(s) nanostructures prepared using themethods described herein display high photoluminescence quantum yield.In some embodiments, the core/shell(s) nanostructures can have aphotoluminescence quantum yield of between 60% and 100%, between 60% and95%, between 60% and 90%, between 60% and 85%, between 60% and 80%,between 60% and 70%, between 70% and 100%, between 70% and 95%, between70% and 90%, between 70% and 85%, between 70% and 80%, between 80% and100%, between 80% and 95%, between 80% to 90%, between 80% and 85%,between 85% and 100%, between 85% and 95%, between 80% and 85%, between85% and 100%, between 85% and 90%, between 90% and 100%, between 90% and95%, or between 95% and 100%. In some embodiments, the core/shell(s)nanostructures prepared using the methods described herein have aphotoluminescence quantum yield of between 60% and 99%. In someembodiments, the core/shell(s) nanostructures prepared using the methodsdescribed herein have a photoluminescence quantum yield of between 70%and 99%.

The photoluminescence spectrum of the core/shell(s) nanostructuresprepared using the methods described herein can cover essentially anydesired portion of the spectrum. In some embodiments, thephotoluminescence spectrum for the core/shell(s) nanostructures havepeak emission wavelength (PWL) between 300 nm and 750 nm, between 300 nmand 650 nm, between 300 nm and 550 nm, between 300 nm and 450 nm,between 450 nm and 750 nm, between 450 nm and 650 nm, between 450 nm and550 nm, between 450 nm and 750 nm, between 450 nm and 650 nm, between450 nm and 550 nm, between 550 nm and 750 nm, between 550 nm and 650 nm,or between 650 nm and 750 nm. In some embodiments, the photoluminescencespectrum for the core/shell(s) nanostructures have PWL of between 400 nmand 500 nm.

The size distribution of the core/shell(s) nanostructures prepared usingthe methods described herein can be relatively narrow. In someembodiments, the photoluminescence spectrum of the population orcore/shell(s) nanostructures prepared using the methods described hereinhave a full width at half maximum of between 10 nm and 60 nm, between 10nm and 40 nm, between 10 nm and 30 nm, between 10 nm and 20 nm, between20 nm and 60 nm, between 20 nm and 40 nm, between 20 nm and 30 nm,between 30 nm and 60 nm, between 30 nm and 40 nm, or between 40 nm and60 nm. In some embodiments, the photoluminescence spectrum of thepopulation or core/shell(s) nanostructures prepared using the methodsdescribed herein have a full width at half maximum of between 10 nm and40 nm. In some embodiments, the photoluminescence spectrum of thepopulation of core/shell(s) nanostructures prepared using the methodsdescribed herein have a full width at half maximum of between 30 nm and45 nm.

Nanostructure Film

In some embodiments, the core/shell(s) nanostructures prepared by themethod described herein are incorporated into a nanostructure film. Insome embodiments, the nanostructure film is incorporated into a quantumdot enhancement film (QDEF).

In some embodiments, the present disclosure provides a nanostructurefilm comprising:

-   -   (a) at least one population of nanostructures, the        nanostructures comprising a core comprising a nanocrystal core;        and at least one shell disposed on the core, wherein at least        one shell comprises ZnS and fluoride; and    -   (b) at least one organic resin.

In some embodiments, the present disclosure provides a nanostructurefilm comprising:

-   -   (a) at least one population of nanostructures, the        nanostructures comprising a core comprising a nanocrystal core;        and at least one shell disposed on the core, wherein at least        one shell comprises ZnS; at least one fluoride bound to the        surface of the nanostructures; and at least one amine bound to        the surface of the nanostructures; and    -   (b) at least one organic resin.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the present disclosure provides a nanostructurefilm comprising:

-   -   (a) at least one population of nanostructures, the        nanostructures comprising a core comprising ZnSe or        ZnSe_(1-x)Te_(x), wherein 0≤x<1, and a first metal fluoride; and        at least one shell disposed on the core, wherein at least one        shell comprises ZnS and optionally a second metal fluoride; and    -   (b) at least one organic resin.

In some embodiments, the present disclosure provides a nanostructurefilm comprising:

-   -   (a) at least one population of nanostructures, the        nanostructures comprising a core comprising InP; and at least        one shell disposed on the core, wherein at least one shell        comprises ZnS or ZnSe; at least one fluoride bound to the        surface of the nanostructure; and at least one amine bound to        the surface of the nanostructure; and    -   (b) at least one organic resin.

In some embodiments, the nanostructure is a quantum dot.

In some embodiments, the core/shell(s) nanostructures are embedded in amatrix. As used herein, the term “embedded” is used to indicate that thenanostructures are enclosed or encased within a matrix material thatmakes up the majority component of the matrix. In some embodiments, thenanostructures are uniformly distributed throughout the matrix material.In some embodiments, the nanostructures are distributed according to anapplication-specific uniformity distribution function.

In some embodiments, the nanostructures can include a homogenouspopulation having sizes that emit in the blue visible wavelengthspectrum, in the green visible wavelength spectrum, or in the redvisible wavelength spectrum. In some embodiments, the nanostructures caninclude a first population of nanostructures having sizes that emit inthe blue visible wavelength spectrum, a second population ofnanostructures having sizes that emit in the green visible wavelengthspectrum, and a third population of nanostructures having sizes thatemit in the red visible wavelength spectrum.

The matrix material can be any suitable host matrix material capable ofhousing nanostructures. Suitable matrix materials can be chemically andoptically compatible with nanostructures and any surrounding packagingmaterials or layers used in applying a nanostructure film to devices.Suitable matrix materials can include non-yellowing optical materialsthat are transparent to both the primary and secondary light, therebyallowing for both primary and secondary light to transmit through thematrix material. Matrix materials can include polymers and organic andinorganic oxides. Suitable polymers for use in the matrix material canbe any polymer known to the ordinarily skilled artisan that can be usedfor such a purpose. The polymer can be substantially translucent orsubstantially transparent. Matrix materials can include, but not limitedto, epoxies, acrylates, norbornene, polyethylene, poly(vinylbutyral):poly(vinyl acetate), polyurea, polyurethanes; silicones andsilicone derivatives including, but not limited to, amino silicone(AMS), polyphenylmethylsiloxane, polyphenylalkylsiloxane,polydiphenylsiloxane, polydialkylsiloxane, silsesquioxanes, fluorinatedsilicones, and vinyl and hydride substituted silicones; acrylic polymersand copolymers formed from monomers including, but not limited to,methylmethacrylate, butylmethacrylate, and laurylmethacrylate;styrene-based polymers such as polystyrene, amino polystyrene (APS), andpoly(acrylonitrile ethylene styrene) (AES); polymers that arecross-linked with bifunctional monomers, such as divinylbenzene;cross-linkers suitable for cross-linking ligand materials, epoxides thatcombine with ligand amines (e.g., APS or polyethylene imine ligandamines) to form epoxy, and the like.

In some embodiments, the matrix material includes scattering microbeadssuch as TiO₂ microbeads, ZnS microbeads, or glass microbeads that canimprove photo conversion efficiency of the nanostructure film. In someembodiments, the matrix material can include light blocking elements.

In some embodiments, the matrix material can have low oxygen andmoisture permeability, exhibit high photo- and chemical-stability,exhibit favorable refractive indices, and adhere to outer surfaces ofthe nanostructures, thus providing an air-tight seal to protect thenanostructures. In another embodiment, the matrix material can becurable with UV or thermal curing methods to facilitate roll-to-rollprocessing.

In some embodiments, a nanostructure film can be formed by mixingnanostructures in a polymer (e.g., photoresist) and casting thenanostructure-polymer mixture on a substrate, mixing the nanostructureswith monomers and polymerizing them together, mixing nanostructures in asol-gel to form an oxide, or any other method known to those skilled inthe art.

In some embodiments, the formation of a nanostructure film can include afilm extrusion process. The film extrusion process can include forming ahomogenous mixture of matrix material and barrier layer coatedcore-shell nanostructures such as nanostructures functionalized with ametal halide and/or a metal carboxylate, introducing the homogenousmixture into a top mounted hopper that feeds into an extruder. In someembodiments, the homogenous mixture can be in the form of pellets. Thefilm extrusion process can further include extruding a nanostructurefilm from a slot die and passing an extruded nanostructure film throughchill rolls. In some embodiments, the extruded nanostructure film canhave a thickness less than about 75 μm, for example, in a range fromabout 70 μm to about 40 μm, about 65 μm to about 40 μm, about 60 μm toabout 40 μm, or about 50 μm to about 40 μm. In some embodiments, thenanostructure film has a thickness less than about 10 μm. In someembodiments, the formation of the nanostructure film can optionallyinclude a secondary process followed by the film extrusion process. Thesecondary process can include a process such as co-extrusion,thermoforming, vacuum forming, plasma treatment, molding, and/orembossing to provide a texture to a top surface of the nanostructurefilm layer. The textured top surface nanostructure film can help toimprove, for example defined optical diffusion property and/or definedangular optical emission property of the nanostructure film.

Nanostructure Molded Article

In some embodiments, the nanostructure composition is used to form ananostructure molded article. In some embodiments, the nanostructuremolded article is a liquid crystal display (LCD) or a light emittingdiode (LED). In some embodiments, the nanostructure composition is usedto form the emitting layer of an illumination device. The illuminationdevice can be used in a wide variety of applications, such as flexibleelectronics, touchscreens, monitors, televisions, cellphones, and anyother high definition displays. In some embodiments, the illuminationdevice is a light emitting diode or a liquid crystal display. In someembodiments, the illumination device is a quantum dot light emittingdiode (QLED). An example of a QLED is disclosed in U.S. patentapplication Ser. No. 15/824,701, which is incorporated herein byreference in its entirety.

In some embodiments, the present disclosure provides a light emittingdiode comprising:

-   -   (a) a first conductive layer;    -   (b) a second conductive layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising a        nanocrystal core; and at least one shell disposed on the core,        wherein at least one shell comprises ZnS and fluoride.

In some embodiments, the present disclosure provides a light emittingdiode comprising:

-   -   (a) a first conductive layer;    -   (b) a second conductive layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising a        nanocrystal core; and at least one shell disposed on the core,        wherein at least one shell comprises ZnS or ZnSe; at least one        fluoride bound to the surface of the nanostructures; and at        least one amine bound to the surface of the nanostructures.

In some embodiments, the present disclosure provides a light emittingdiode comprising:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising ZnSe        or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and a first metal fluoride;        and at least one shell disposed on the core, wherein at least        one shell comprises ZnS and optionally a second metal fluoride.

In some embodiments, the present disclosure provides a light emittingdiode comprising:

-   -   (a) a first barrier layer;    -   (b) a second barrier layer; and    -   (c) an emitting layer between the first barrier layer and the        second barrier layer, wherein the emitting layer comprises a        population of nanostructures comprising a core comprising InP;        and at least one shell disposed on the core, wherein at least        one shell comprises ZnS or ZnSe; at least one fluoride bound to        the surface of the nanostructures; and at least one amine bound        to the surface of the nanostructures.

In some embodiments, the emitting layer is a nanostructure film.

In some embodiments, the light emitting diode comprises a firstconductive layer, a second conductive layer, and an emitting layer,wherein the emitting layer is arranged between the first conductivelayer and the second conductive layer. In some embodiments, the emittinglayer is a thin film.

In some embodiments, the light emitting diode comprises additionallayers between the first conductive layer and the second conductivelayer such as a hole injection layer, a hole transport layer, and anelectron transport layer. In some embodiments, the hole injection layer,the hole transport layer, and the electron transport layer are thinfilms. In some embodiments, the layers are stacked on a substrate.

When voltage is applied to the first conductive layer and the secondconductive layer, holes injected at the first conductive layer move tothe emitting layer via the hole injection layer and/or the holetransport layer, and electrons injected from the second conductive layermove to the emitting layer via the electron transport layer. The holesand electrons recombine in the emitting layer to generate excitons.

Quantum Dot on Glass LCD Display Device

In some embodiments, the nanostructure film is incorporated into aquantum dot on glass LCD display device. A LCD display device caninclude a nanostructure film formed directly on a light guide plate(LGP) without necessitating an intermediate substrate or barrier layer.In some embodiments, a nanostructure film can be a thin film. In someembodiments, a nanostructure film can have a thickness of 500 μm orless, 100 μm or less, or 50 μm or less. In some embodiments, ananostructure film is a thin film having a thickness of about 15 μm orless.

A LGP can include an optical cavity having one or more sides, includingat least a top side, comprising glass. Glass provides excellentresistance to impurities including moisture and air. Moreover, glass canbe formed as a thin substrate while maintaining structural rigidity.Therefore, a LGP can be formed at least partially of a glass surface toprovide a substrate having sufficient barrier and structural properties.

In some embodiments, a nanostructure film can be formed on a LGP. Insome embodiments, the nanostructure film comprises a population ofnanostructures embedded in a matrix material, such as a resin. Ananostructure film can be formed on a LGP by any method known in theart, such as wet coating, painting, spin coating, or screen printing.After deposition, a resin of a nanostructure film can be cured. In someembodiments a resin of one or more nanostructure films can be partiallycured, further processed and then finally cured. The nanostructure filmscan be deposited as one layer or as separate layers, and the separatelayers can comprise varying properties. The width and height of thenanostructure films can be any desired dimensions, depending on the sizeof the viewing panel of the display device. For example, thenanostructure films can have a relatively small surface area in smalldisplay device embodiments such as watches and phones, or thenanostructure films can have a large surface area for large displaydevice embodiments such as TVs and computer monitors.

In some embodiments, an optically transparent substrate is formed on ananostructure film by any method known in the art, such as vacuumdeposition, vapor deposition, or the like. An optically transparentsubstrate can be configured to provide environmental sealing to theunderlying layers and/or structures of the nanostructure film. In someembodiments, light blocking elements can be included in the opticallytransparent substrate. In some embodiments, light blocking elements canbe included in a second polarizing filter, which can be positionedbetween the substrate and the nanostructure film. In some embodiments,light blocking elements can be dichroic filters that, for example, canreflect the primary light (e.g., blue light, UV light, or combination ofUV light and blue light) while transmitting the secondary light. Lightblocking elements can include specific UV light filtering components toremove any unconverted UV light from the red and green sub-pixels,and/or the UV light from the blue sub-pixels.

On-Chip and Near Chip Placement of Quantum Dots

In some embodiments, the nanostructures are incorporated into displaydevices by “on-chip” placements. As used herein, “on-chip” refers toplacing nanostructures into an LED cup. In some embodiments, thenanostructures are dissolved in a resin or a fluid to fill the LED cup.

In some embodiments, the nanostructures are incorporated into displaydevices by “near-chip” placements. As used herein, “near-chip” refers tocoating the top surface of the LED assembly with nanostructures suchthat the outgoing light passes through the nanostructure film.

Display Device with Nanostructure Color Conversion Layer

In some embodiments, the present invention provides a display devicecomprising:

-   -   (a) a display panel to emit a first light;    -   (b) a backlight unit configured to provide the first light to        the display panel; and    -   (c) a color filter comprising at least one pixel region        comprising a color conversion layer.

In some embodiments, the color filter comprises at least 1, 2, 3, 4, 5,6, 7, 8, 9, or 10 pixel regions. In some embodiments, when blue light isincident on the color filter, red light, white light, green light,and/or blue light may be respectively emitted through the pixel regions.In some embodiments, the color filter is described in U.S. Patent Appl.Publication No. 2017/153366, which is incorporated herein by referencein its entirety.

In some embodiments, each pixel region includes a color conversionlayer. In some embodiments, a color conversion layer comprisesnanostructures described herein configured to convert incident lightinto light of a first color. In some embodiments, the color conversionlayer comprises nanostructures described herein configured to convertincident light into blue light.

In some embodiments, the display device comprises 1, 2, 3, 4, 5, 6, 7,8, 9, or 10 color conversion layers. In some embodiments, the displaydevice comprises 1 color conversion layer comprising the nanostructuresdescribed herein. In some embodiments, the display device comprises 2color conversion layers comprising the nanostructures described herein.In some embodiments, the display device comprises 3 color conversionlayers comprising the nanostructures described herein. In someembodiments, the display device comprises 4 color conversion layerscomprising the nanostructures described herein. In some embodiments, thedisplay device comprises at least one red color conversion layer, atleast one green color conversion layer, and at least one blue colorconversion layer.

In some embodiments, the color conversion layer has a thickness betweenabout 3 μm and about 10 μm, about 3 μm and about 8 μm, about 3 μm andabout 6 μm, about 6 μm and about 10 μm, about 6 μm and about 8 μm, orabout 8 μm and about 10 μm. In some embodiments, the color conversionlayer has a thickness between about 3 μm and about 10 μm.

The nanostructure color conversion layer can be deposited by anysuitable method known in the art, including but not limited to painting,spray coating, solvent spraying, wet coating, adhesive coating, spincoating, tape-coating, roll coating, flow coating, inkjet printing,photoresist patterning, drop casting, blade coating, mist deposition, ora combination thereof. In some embodiments, the nanostructure colorconversion layer is deposited by photoresist patterning. In someembodiments, nanostructure color conversion layer is deposited by inkjetprinting.

Inkjet Printing

The formation of thin films using dispersions of nanostructures inorganic solvents is often achieved by coating techniques such as spincoating. However, these coating techniques are generally not suitablefor the formation of thin films over a large area and do not provide ameans to pattern the deposited layer and thus, are of limited use.Inkjet printing allows for precisely patterned placement of thin filmson a large scale at low cost. Inkjet printing also allows for precisepatterning of nanostructure layers, allows printing pixels of a display,and eliminates photopatterning. Thus, inkjet printing is very attractivefor industrial application—particularly in display applications.

Solvents commonly used for inkjet printing are dipropylene glycolmonomethyl ether acetate (DPMA), polyglycidyl methacrylate (PGMA),diethylene glycol monoethyl ether acetate (EDGAC), and propylene glycolmethyl ether acetate (PGMEA). Volatile solvents are also frequently usedin inkjet printing because they allow rapid drying. Volatile solventsinclude ethanol, methanol, 1-propanol, 2-propanol, acetone, methyl ethylketone, methyl isobutyl ketone, ethyl acetate, and tetrahydrofuran.Conventional nanostructures generally cannot be dissolved in thesesolvents. However, the increased hydrophilicity of the nanostructurescomprising poly(alkylene oxide) ligands allows for increased solubilityin these solvents.

In some embodiments, the nanostructures described herein used for inkjetprinting are dispersed in a solvent selected from DPMA, PGMA, EDGAC,PGMEA, ethanol, methanol, 1-propanol, 2-propanol, acetone, methyl ethylketone, methyl isobutyl ketone, ethyl acetate, tetrahydrofuran,chloroform, chlorobenzene, cyclohexane, hexane, heptane, octane,hexadecane, undecane, decane, dodecane, xylene, toluene, benzene,octadecane, tetradecane, butyl ether, or combinations thereof. In someembodiments, the nanostructures comprising a poly(alkylene oxide)ligands described herein used for inkjet printing are dispersed in asolvent selected from DPMA, PGMA, EDGAC, PGMEA, ethanol, methanol,1-propanol, 2-propanol, acetone, methyl ethyl ketone, methyl isobutylketone, ethyl acetate, tetrahydrofuran, or combinations thereof.

In order to be applied by inkjet printing or microdispensing, the inkjetcompositions comprising nanostructures should be dissolved in a suitablesolvent. The solvent must be able to disperse the nanostructurecomposition and must not have any detrimental effect on the chosen printhead.

In some embodiments, the inkjet composition further comprises one ormore additional components such as surface-active compounds, lubricatingagents, wetting agents, dispersing agents, hydrophobing agents, adhesiveagents, flow improvers, defoaming agents, deaerators, diluents,auxiliaries, colorants, dyes, pigments, sensitizers, stabilizers, andinhibitors.

In some embodiments, the nanostructure compositions described hereincomprise by weight of the inkjet composition between about 0.01% andabout 20%. In some embodiments, the nanostructures comprisingpoly(alkylene oxide) ligands comprise by weight of the inkjetcomposition between about 0.01% and about 20%, about 0.01% and about15%, about 0.01% and about 10%, about 0.01% and about 5%, about 0.01%and about 2%, about 0.01% and about 1%, about 0.01% and about 0.1%,about 0.01% and about 0.05%, about 0.05% and about 20%, about 0.05% andabout 15%, about 0.05% and about 10%, about 0.05% and about 5%, about0.05% and about 2%, about 0.05% and about 1%, about 0.05% and about0.1%, about 0.1% and about 20%, about 0.1% and about 15%, about 0.1% andabout 10%, about 0.1% and about 5%, about 0.1% and about 2%, about 0.1%and about 1%, about 0.5% and about 20%, about 0.5% and about 15%, about0.5% and about 10%, about 0.5% and about 5%, about 0.5% and about 2%,about 0.5% and about 1%, about 1% and about 20%, about 1% and about 15%,about 1% and about 10%, about 1% and about 5%, about 1% and about 2%,about 2% and about 20%, about 2% and about 15%, about 2% and about 10%,about 2% and about 5%, about 5% and about 20%, about 5% and about 15%,about 5% and about 10%, about 10% and about 20%, about 10% and about15%, or about 15% and 20%.

In some embodiments, the inkjet composition comprising a nanostructureor a nanostructure composition described herein is used in theformulation of an electronic device. In some embodiments, the inkjetcomposition comprising a nanostructure or a nanostructure compositiondescribed herein is used in the formulation of an electronic deviceselected from the group consisting of a nanostructure film, a displaydevice, a lighting device, a backlight unit, a color filter, a surfacelight-emitting device, an electrode, a magnetic memory device, and abattery. In some embodiments, the inkjet composition comprising ananostructure composition described herein is used in the formulation ofa light-emitting device.

Illumination Devices with Improved Properties

In some embodiments, an illumination device prepared usingnanostructures of the present disclosure shows an EQE of between about1.5% and about 20%, about 1.5% and about 15%, about 1.5% and about 12%,about 1.5% and about 10%, about 1.5% and about 8%, about 1.5% and about4%, about 1.5% and about 3%, about 3% and about 20%, about 3% and about15%, about 3% and about 12%, about 3% and about 10%, about 3% and about8%, about 8% and about 20%, about 8% and about 15%, about 8% and about12%, about 8% and about 10%, about 10% and about 20%, about 10% andabout 15%, about 10% and about 12%, about 12% and about 20%, about 12%and about 15%, or about 15% and about 20%. In some embodiments, anillumination device prepared using nanostructures of the presentdisclosure shows an EQE of between about 1.5% and about 15%. In someembodiments, an illumination device prepared using nanostructures of thepresent disclosure shows an EQE of about 5%. In some embodiments, theillumination device is a light emitting diode.

In some embodiments, an illumination device prepared using thenanostructures of the present disclosure shows an improved lifetime. Insome embodiments, an illumination device prepared using thenanostructures of the present disclosure reaches 50% of initialluminance of 500 cd/m² (nits) (T₅₀) after between about 1 second andabout 100 seconds, 1 about second and about 50 seconds, about 1 secondand about 40 seconds, about 1 second and about 30 seconds, about 1second and about 20 seconds, about 1 second and about 10 seconds, about10 seconds and about 100 seconds, about 10 seconds and about 50 seconds,about 10 seconds and about 40 seconds, about 10 seconds and about 30seconds, about 10 seconds and about 20 seconds, about 20 seconds andabout 100 seconds, about 20 seconds and about 50 seconds, about 20seconds and about 40 seconds, about 20 seconds and about 30 seconds,about 30 seconds and about 40 seconds, about 40 seconds and about 100seconds, about 40 seconds and about 50 seconds, or about 50 seconds andabout 100 seconds. In some embodiments, an illumination device preparedusing the nanostructures of the present disclosure reaches 50% ofinitial luminance of 500 cd/m² (nits) (T₅₀) after between about 19second and about 35 seconds.

In some embodiments, the time for an illumination device prepared usingthe nanostructure of the present disclosure with fluoride in the shellto reach 50% of initial luminance of 500 cd/m² (nits) (T₅₀) is at leastabout three times longer than the T₅₀ for an electroluminescent devicecomprising the corresponding nanostructure without any fluoride in theshell.

EXAMPLES

The following examples are illustrative and non-limiting, of theproducts and methods described herein. Suitable modifications andadaptations of the variety of conditions, formulations, and otherparameters normally encountered in the field and which are obvious tothose skilled in the art in view of this disclosure are within thespirit and scope of the invention.

Example 1

Synthesis of ZnSe_(1-x)Te_(x) Alloy Nanocrystals Using TOPTe Precursor

Preparation of TOPTe precursor: the Te precursor mixture was prepared byfirst diluting trioctylphosphine telluride (1 M Te, 230 μL) with 2.5 mLdried and distilled oleylamine. Lithium triethylborohydride (1 M in THF,230 μL) was added to this solution which resulted in a deeply purplesolution. Finally, zinc oleate (0.5 M in trioctylphosphine (TOP), 460μL) was added which resulted in a colorless opaque viscous gel whichcould be drawn into a syringe.

Oleylamine (15 mL) was added to a 100 mL three neck flask and degassedunder vacuum at 110° C. for 30 minutes. Then the mixture was heated to300° C. under nitrogen flow. Once this temperature was reached, asolution of trioctylphosphine selenide (TOPSe, 2.7 mmol) anddiphenylphosphine (225 μL) in TOP (2.9 mL total) was added to the flask.Once the temperature rebounded to 300° C., the TOPTe precursor describedabove and a solution of diethyl zinc (295 μL) in TOP (1 mL) were quicklyinjected from separate syringes. The temperature was set to 280° C. andafter 5 minutes the infusion of a solution of diethylzinc (294 μL) andTOPSe (4.4 mmol) in TOP (3.8 mL total) was started at a rate of 0.5mL/min until complete addition of the full 3.8 mL. After the precursorinfusion was finished, the reaction mixture was held at 280° C. for 5minutes and then cooled to room temperature. The growth solution wasdiluted with an equal volume of toluene (40 mL), and the nanocrystalswere precipitated by addition of ethanol (120 mL). After centrifugationthe supernatant was discarded, and the nanocrystals were redispersed inhexane (5 mL). The concentration was measured as the dry weight byevaporating the solvent off an aliquot. The dried material was furthersubjected to thermogravimetric analysis to determine the ZnSe content.

Example 2 Synthesis of ZnSe Nanocrystals

ZnSe nanocrystals were prepared using the method of Example 1 withoutthe injection of the TOPTe precursor.

Example 3

Synthesis of ZnSe_(1-x)Te_(x)/ZnSe Buffered Nanocrystals

A ZnSe buffer layer on ZnSe_(1-x)Te_(x) nanocrystals of 4.0 nm averagediameter with a target shell thickness of 4 monolayers (ML) ZnSe wasprepared.

A 100 mL three neck flask was charged with zinc oleate (6.23 g), lauricacid (3.96 g), trioctylphosphine oxide (4.66 g), and TOP (9.4 mL). Theflask was subjected to three vacuum and nitrogen backfill cycles beforeheating to 100° C. and degassing for 30 minutes. The reaction mixturewas placed under a blanket of nitrogen and a solution ofZnSe_(1-x)Te_(x) cores (4.0 mL, 28.0 mg/mL in hexane) mixed with TOPSe(1.8 mL of 0.3 M selenium in TOP) was added to the flask. The flask wasevacuated for 2 minutes and then heated to 310° C. under nitrogen flow.Once this temperature was reached, the slow infusion of TOPSe (10.4 mL,0.3 M in TOP) with a rate of 0.325 mL/min was started. After theselenium infusion was finished, the reaction was held at 310° C. for 10minutes and then cooled to room temperature. The reaction mixture wasdiluted with toluene (45 mL). The core/shell nanocrystals wereprecipitated by addition of ethanol (135 mL) and then isolated bycentrifugation, decantation of the supernatant, and redispersion of thenanocrystals in hexane (5 mL). This solution was filtered through a PTFE0.22 μm syringe filter and the concentration was measured as the dryweight by evaporating the solvent off an aliquot. The dried material wasfurther subjected to thermogravimetric analysis to determine the ZnSecontent.

Example 4

Synthesis of ZnSe_(1-x)Te_(x)/ZnSe Buffered Nanocrystals with FluoridePassivation

The procedure is the same as the method outlined in Example 3, with theaddition of 0.78 mmol of zinc fluoride, zirconium fluoride, or hafniumfluoride prior to the initial three vacuum and nitrogen backfill cycles.

Example 5 Synthesis of ZnSe/ZnSe Buffered Nanocrystals

A ZnSe buffer layer on a ZnSe nanocrystals of 4.0 nm average diameterwith a target shell thickness of 4 monolayers (ML) ZnSe was prepared.

A 500 mL three neck flask was charged with zinc oleate (27.63 g), lauricacid (17.54 g), trioctylphosphine oxide (18.00 g), and TOP (36.0 mL).The flask was then subjected to three vacuum and nitrogen backfillcycles before heating to 100° C. and degassing for 30 minutes. Thereaction mixture was placed under a blanket of nitrogen and a solutionof ZnSe cores (2.0 mL, 216.0 mg/mL in hexane) was added to the flask.The flask was evacuated for 2 minutes and then heated to 310° C. undernitrogen flow. Once this temperature was reached, the slow infusion ofTOPSe (25.3 mL, 0.3 M in TOP) with a rate of 0.720 mL/min was started.After the selenium infusion was finished, the reaction was held at 310°C. for 10 minutes and then cooled to room temperature. The reactionmixture was diluted with toluene (95 mL). The core/shell nanocrystalswere precipitated by addition of ethanol (190 mL) and then isolated bycentrifugation, decantation of the supernatant, and redispersion of thenanocrystals in hexane (7 mL). This solution was filtered through a PTFE0.22 μm syringe filter and the concentration was measured as the dryweight by evaporating the solvent off an aliquot. The dried material wasfurther subjected to thermogravimetric analysis to determine the ZnSecontent.

Example 6

Synthesis of ZnSe/ZnSe Buffered Nanocrystals with Fluoride Passivation

The procedure is the same as the method outlined in Example 5, with theaddition of 3.0 mmol of zinc fluoride, zirconium fluoride, or hafniumfluoride prior to the initial three vacuum and nitrogen backfill cycles.

Example 7

Synthesis of ZnSe_(1-x)Te_(x)/ZnSe/ZnS Core/Shell Nanocrystals

A ZnS shell on ZnSe_(1-x)Te_(x)/ZnSe nanocrystals of 6.1 nm averagediameter with a target shell thickness of 4 monolayers (ML) ZnS wasprepared.

A 25 mL three neck flask was charged with zinc oleate (375 mg), lauricacid (240 mg), trioctylphosphine oxide (281 mg), and TOP (0.566 mL). Theflask was then subjected to three vacuum and nitrogen backfill cyclesbefore heating to 100° C. and degassing for 30 minutes. The reactionmixture was placed under a blanket of nitrogen and a solution ofZnSe_(1-x)Te_(x)/ZnSe nanocrystals of Example 3 or Example 4 (0.30 mL,216.0 mg/mL in hexane) mixed with zinc oleate/TOPS (0.064 ml of 2.0 Msulfur in TOP+0.254 ml 0.5 M zinc oleate in TOP) was added to the flask.The flask was evacuated for 2 minutes and then heated to 310° C. undernitrogen flow. Once this temperature was reached, the slow infusion ofzinc oleate/TOPS (9.5 mL, 0.3 M in TOP) with a rate of 0.103 mL/min wasstarted. After the sulfur infusion was finished, the reaction was heldat 310° C. for 10 minutes and then cooled to room temperature. Thereaction mixture was diluted with toluene (5 mL). The core/shellnanocrystals were precipitated by addition of ethanol (10 mL) and thenisolated by centrifugation, decantation of the supernatant, andredispersion of the nanocrystals in hexane (5 mL). The precipitation wasrepeated once with ethanol (10 mL), and the nanocrystals were finallyredispersed in octane (3 mL). This solution was filtered through a PTFE0.22 μm syringe filter and the concentration was adjusted to 18 mg/mLafter measuring the dry weight of an aliquot.

Example 8 Synthesis of ZnSe/ZnSe/ZnS Core/Shell Nanocrystals

The procedure is the same as the method outlined in Example 7, exceptthat ZnSe/ZnSe nanocrystals of Example 5 or Example 6 were injected inplace of the ZnSe_(1-x)Te_(x)/ZnSe nanocrystals.

Example 9

Synthesis of ZnSe/ZnSe/ZnS Core/Shell Nanocrystals with FluoridePassivation

The procedure is the same as the method outlined in Example 8, exceptthat the flask was also charged with anhydrous zinc fluoride (1.94mmol), or 0.9 mmol of either hafnium or zirconium fluoride, prior to theinitial three vacuum and nitrogen backfill cycles.

Example 10

Synthesis of ZnSe_(1-x)Te_(x)/ZnSe/ZnS Core/Shell Nanocrystals withFluoride Passivation

The procedure is the same as the method outlined in Example 7, with theaddition of 3.0 mmol of zinc fluoride, zirconium fluoride, or hafniumfluoride, prior to the initial three vacuum and nitrogen backfillcycles.

Example 11

Synthesis of ZnSe/ZnSe/ZnS Core/Shell Nanocrystals with IncreasedFluoride Passivation

The procedure is the same as the method outlined in Example 9, exceptthat the flask was also charged with anhydrous zinc fluoride (634.0 mg),prior to the initial three vacuum and nitrogen backfill cycles.

Example 12 Photoluminescent Properties of Nanocrystals Prepared UsingFluorides During Shelling Reaction

The solution photoluminescence spectra of the ZnSe/ZnS core/shell andZnSeTe/ZnSe/ZnS core/shell/shell quantum dots prepared in the presenceof ZnF₂ during shelling reaction are shown in TABLE 1. As shown in TABLE1, the resultant core/shell(s) quantum dots with a well-passivatedsurface exhibit high quantum yield (QY) and narrow full width athalf-maximum (FWHM).

As shown in TABLE 1, increasing the material loading of ZnF₂ in theshelling reaction from 4 mol. eq (Sample B) to 14 mol. eq. (Sample C)resulted in better surface coverage which in turn unexpectedly resultedin a higher QY and narrower FWHM.

Incorporation of fluorides during the shell growth also resulted in achange of morphology of the ZnS shelled quantum dots. Instead of thequasi-spherical particles synthesized using standard shell growthconditions (FIG. 2 and FIG. 5), particles with cubic shape were obtainedin the presence of ZnF₂, regardless of the loading level of ZnF₂ (FIG.3, FIG. 4, and FIG. 6). These cubic particles also demonstratesignificantly less roll-off at higher luminance in electroluminescentdevices. For example, FIG. 7 is a scatterplot of external quantumefficiency (EQE) versus luminance (nits) for ZnSe/ZnS quantum dots withstandard ligands (no ZnF₂) (Sample A), ZnSe/ZnS quantum dots treatedwith 4 mol. eq. ZnF₂ (Sample B), and ZnSe/ZnS quantum dots treated with14 mol. eq. ZnF₂ (Sample C). The improved roll-off is indicative of theimproved surface passivation and electrochemical stability of the ZnF₂ligands.

Furthermore, the presence of fluorine in the final core/shell quantumdots prepared in the presence of ZnF₂ during shelling reaction can beconfirmed by X-ray photoelectron spectroscopy (XPS). FIG. 8 shows theoverall atomic composition of Example B with 1.9% of all atoms beingfluorine and with the measured F:Zn ratio being 0.13. FIGS. 9A and 9Bcompare the high resolution XPS spectra of the fluorine is regionbetween Sample A and Sample B. A significant signal for Sample B wasobserved in FIG. 9B.

TABLE 1 PWL FWHM Sample Composition Method (nm) (nm) QY A ZnSe/ZnS Nofluoride 433.1 14.5 79% B ZnSe/ZnS ZnF₂ 4 eq 430 13.4 66% (anhydrous) CZnSe/ZnS ZnF₂ 14 eq 430.2 12.8 76% (anhydrous) D ZnSeTe/ZnSe/ZnS Nofluoride 453.5 34.5 60% E ZnSeTe/ZnSe/ZnS ZnF₂ 453.4 37.6 61%(anhydrous)

Example 13 Electroluminescent Devices Prepared

Devices were prepared by a combination of spin coating and thermalevaporation. Firstly, the hole injection materialpoly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) (50nm) was spin coated onto a UV-ozone treated indium tin oxide (ITO)substrate and baked for 15 minutes at 200° C. The devices weretransferred to an inert atmosphere and the hole transport materialN,N′-di(naphthalen-1-yl)-N,N′-bis(4-vinylphenyl)biphenyl-4,4′-diamine(VNPB) (20 nm) was deposited by spin coating and baked at 200° C. for 15minutes. A solution of either ZnSe/ZnS or ZnSe_(1-x)Te_(x)/ZnSe/ZnS QDswas deposited by spin coating (with no resin used in the emissivelayer), followed by spin coating of the electron transport materialZnMgO (20 nm). An Al cathode (150 nm) was then deposited by thermalevaporation followed by encapsulation of the device using a cap-glass,getter, and epoxy resin.

Example 14 Electroluminescent Properties of Devices Prepared UsingQuantum Dots of Samples A-E

The electroluminescence spectra of devices comprising ZnSe/ZnScore/shell and ZnSeTe/ZnSe/ZnS core/shell/shell quantum dots prepared inthe presence of ZnF₂ during shelling reaction (Samples A-E in Table 1)are shown in TABLE 2. As shown in TABLE 2, the electroluminescentlifetime (T₅₀ at 500 cd/m²) was increased unexpectedly by a factor of2-6 in quantum dots prepared in the presence of ZnF₂.

As shown in TABLE 2, increasing the material loading of ZnF₂ in theshelling reaction from 4 mol. eq (Device with Sample B) to 14 mol. eq.(Device with Sample C) resulted in better surface coverage which in turnled unexpectedly to a significantly longer lifetime.

TABLE 2 T₅₀ at PWL 500 cd/m² Max Device Composition Method (nm) (sec)EQE Sample A ZnSe/ZnS No fluoride 436 6.1 4.1% Sample B ZnSe/ZnS ZnF₂4eq 432 19.6 3.0% (anhydrous) Sample C ZnSe/ZnS ZnF₂ 14eq 436 35.7 4.0%(anhydrous) Sample D ZnSeTe/ZnSe/ZnS No fluoride 460 14.4 2.3% Sample EZnSeTe/ZnSe/ZnS ZnF₂ 456 40.1 2.3% (anhydrous)

Example 15 Photoluminescent Properties of Nanocrystals Prepared UsingVarious Fluorides During Shelling Reaction and ElectroluminescentProperties of Devices Prepared Thereof

The solution photoluminescence spectra of the ZnSe/ZnS core/shell andZnSeTe/ZnSe/ZnS core/shell/shell quantum dots prepared in the presenceof ZnF₂ during shelling reaction (Samples A-E) and in the presence ofother fluoride sources are shown in TABLE 3.

TABLE 3 PWL FWHM Sample Composition Method (nm) (nm) QY A ZnSe/ZnS Nofluoride 433.1 14.5 79% B ZnSe/ZnS ZnF₂ 4eq 430 13.4 66% (anhydrous) CZnSe/ZnS ZnF₂ 14eq 430.2 12.8 76% (anhydrous) D ZnSeTe/ZnSe/ZnS Nofluoride 453.5 34.5 60% E ZnSeTe/ZnSe/ZnS ZnF₂ 453.4 37.6 61%(anhydrous) F ZnSe/ZnS TBAPF₆ 403.9 20.3 11% G ZnSe/ZnS alloy HF & ZnCl₂425.2 16.5 89% H ZnSe/ZnS alloy HF 429.4 15.4 86% I ZnSe/ZnS alloy HF &DCE 426.4 18.5 83%

The electroluminescence spectra of devices (Device A-I) comprisingquantum dots of Samples A-I in Table 3, respectively, are shown in TABLE4.

TABLE 4 T₅₀ at PWL 500 cd/m² Max Device Composition Method (nm) (sec)EQE Sample A ZnSe/ZnS No fluoride 436 6.1 4.1% Sample B ZnSe/ZnS ZnF₂4eq 432 19.6 3.0% (anhydrous) Sample C ZnSe/ZnS ZnF₂ 14eq 436 35.7 4.0%(anhydrous) Sample D ZnSeTe/ZnSe/ No fluoride 460 14.4 2.3% ZnS Sample EZnSeTe/ZnSe/ ZnF₂ 456 40.1 2.3% ZnS (anhydrous) Sample F ZnSe/ZnS TBAPF₆420 1.7 0.09% Sample G ZnSe/ZnS alloy HF & ZnCl₂ 432 39.7 0.07% Sample HZnSe/ZnS alloy HF 436 14.7 3.4% Sample I ZnSe/ZnS alloy HF & DCE 43210.9 1.8%

Example 16 Photoluminescent Properties of Nanocrystals Prepared UsingMetal Fluorides During Core Buffer Growth/Shell Reaction andElectroluminescent Properties of Devices Prepared Thereof

The solution photoluminescence spectra of the ZnSe/ZnS core/shell andZnSeTe/ZnSe/ZnS core/shell/shell quantum dots prepared in the presenceof Group IV fluorides during core buffer growth/shell reaction are shownin TABLE 5. As shown in TABLE 5, the resultant core/shell(s) quantumdots with a well-passivated surface exhibit high quantum yield (QY) andnarrow full width at half-maximum (FWHM).

TABLE 5 PWL FWHM Sample Composition Method (nm) (nm) QY J ZnSe/ZnS Nofluoride 433.1 14.5 79% K ZnSe/ZnS ZrF₄ Core Only 433.4 15.9 79% LZnSe/ZnS ZrF₄ Core & 431.3 16.0 85% Shell M ZnSeTe/ZnSe/ZnS No fluoride446.2 19.2 47% N ZnSeTe/ZnSe/ZnS ZrF₄ Core Only 447.2 21.3 53% OZnSeTe/ZnSe/ZnS ZrF₄ Core & 445.8 22.2 59% Shell

The electroluminescence spectra of devices comprising ZnSe/ZnScore/shell quantum dots (Samples J and K in Table 5) are shown in TABLE6. As shown in TABLE 6, the electroluminescent lifetime (T₅₀ at 500cd/m²) was increased significantly in quantum dots prepared in thepresence of ZrF₄ in the core (Device with Sample K).

TABLE 6 T₅₀ at PWL 500 cd/m² Max Device Composition Method (nm) (sec)EQE Sample J ZnSe/ZnS No fluoride 436 98.4 8.3% Sample K ZnSe/ZnS ZrF₄Core Only 436 186 11.3%

Example 17 Photoluminescent Properties of Nanocrystals Prepared UsingMetal Fluorides During Core Buffer Growth/Shell Reaction andElectroluminescent Properties of Devices Prepared Thereof

The solution quantum yield of the ZnSe/ZnS core/shell quantum dotsprepared in the presence of metal fluorides during core buffergrowth/shell reaction, and the electroluminescence spectra of devicescomprising these quantum dots are shown in TABLE 7 (FIG. 10).

TABLE 7 T₅₀ at Max 500 cd/m² Sample Composition Method QY EQE (sec) PZnSe/ZnS No fluoride 79.8% 5.3% 7.2 Q ZnSe/ZnS ZnF₂ Shell Only 66.0%3.0% 19.6 R ZnSe/ZnS HfF₄ Shell Only 77.8% 4.3% 25.7 S ZnSe/ZnS ZrF₄Shell Only 74.8% 4.1% 18.9 T ZnSe/ZnS ZnF₂ Core Only 63.7% 4.1% 7.2 UZnSe/ZnS HfF₄ Core Only 83.2% 5.8% 7.5 V ZnSe/ZnS ZrF₄ Core Only 79.2%5.3% 10.1 W ZnSe/ZnS ZnF₂ Core & Shell 78.2% 4.0% 35.2 X ZnSe/ZnS HfF₄Core & Shell 81.7% 5.3% 23.3 Y ZnSe/ZnS ZrF₄ Core & Shell 85.2% 5.3% 30

As shown in TABLE 7, as compared to baseline control Sample P, retentionof baseline EQE was observed in all ZnSe cores treated with metalfluorides (Samples T-Y). In addition, a significant and unexpectedincrease in device lifetime (by an order of 2-5) was observed in SamplesQ-S and W—Y where metal fluorides were present in the shelling reaction.Moreover, the combination of metal fluorides in both core and shellresults in superior quantum dots (Samples W-Y) with longer operatinglifetime in the electroluminescent devices without compromising EQE.

Example 18 Quantum Dot Synthesis

Quantum dots used in Examples 19-25 were synthesized using proceduresdescribed in U.S. Patent Appl. Publication No. 2017/0066965 (ZnSe/ZnSquantum dots), U.S. Patent Appl. Publication No. 2017/0306227(InP/ZnSe/ZnS quantum dots), or U.S. Provisional Appl. No. 62/677,853(ZnSe_(1-x)Te_(x)/ZnSe/ZnS quantum dots), which are incorporated byreference in their entireties. The as-synthesized quantum dots werecapped with zinc oleate ligands as their native ligands.

Example 19 TBAF and Octylamine Treatment of InP/ZnSe/ZnS Quantum Dots(Sample Z)

10 mg of tetrabutylammonium fluoride trihydrate (TBAF), 13 mg ofdidodecyldimethylammonium chloride, and 8 mg of octylamine weredissolved in 1.8 mL of toluene. Green-emitting InP/ZnSe/ZnS quantum dots(18 mg, 0.43 mL of a 42 mg/mL stock solution in octane) comprising zincoleate native ligands were added to this solution. The mixture wasstirred at 70° C. for 60 minutes. The quantum dots comprising TBAFligands were isolated by precipitation with acetonitrile (1.2 mL) andredispersed in octane (0.5 mL). The octane dispersion was used foroptical characterization.

Example 20 Octylamine Treatment of InP/ZnSe/ZnS Quantum Dots (Sample AA)

13 mL of didodecyldimethylammonium chloride and 8 mg of octylamine weredissolved in 1.8 mL of toluene. Green-emitting InP/ZnSe/ZnS quantum dots(18 mg, 0.43 mL of a 42 mg/mL stock solution in octane) comprising zincoleate native ligands were added to this solution. The mixture wasstirred at 70° C. for 60 minutes. The resulting quantum dots wereisolated by precipitation with acetonitrile (1.2 mL) and redispersed inoctane (0.5 mL). The octane dispersion was used for opticalcharacterization.

Example 21 TBAF Treatment of InP/ZnSe/ZnS Quantum Dots (Sample AB)

10 mg of tetrabutylammonium fluoride trihydrate and 13 mg ofdidodecyldimethylammonium chloride were dissolved in 1.8 mL of toluene.Green-emitting InP/ZnSe/ZnS quantum dots (18 mg, 0.43 mL of a 42 mg/mLstock solution in octane) comprising zinc oleate native ligands wereadded to this solution. The mixture was stirred at 70° C. for 60minutes. The quantum dots comprising TBAF ligands were isolated byprecipitation with acetonitrile (1.2 mL) and redispersed in octane (0.5mL). The octane dispersion was used for optical characterization.

Example 22 Excess Octylamine Treatment of InP/ZnSe/ZnS Quantum Dots(Samples AC and AD)

Excess octylamine (10 mg) was added to 0.1 mL of the final octanesolutions prepared in Example 19 (using TBAF and octylamine) and Example20 (using only octylamine). These mixtures were directly used foroptical characterization.

Example 23

Photoluminescent Properties of Nanocrystals after Fluoride and/or AmineTreatment and Electroluminescent Properties of Devices Prepared Thereof

The solution quantum yield, photoluminescence, and full-width athalf-maximum values of InP/ZnSe/ZnS quantum dots prepared with andwithout fluoride treatment are shown in TABLE 8.

TABLE 8 QY PWL FWHM Sample Composition Method (%) (nm) (nm) ZInP/ZnSe/ZnS TBAF and Octylamine 74.6 534.7 37.2 AA InP/ZnSe/ZnSOctylamine Only 66.5 533.7 37.3 AB InP/ZnSe/ZnS TBAF Only 76.3 534.037.2 AC InP/ZnSe/ZnS TBAF and Excess 70.2 535.1 38.4 Octylamine ADInP/ZnSe/ZnS No TBAF and Excess 54.2 536.1 39.4 Octylamine

Example 24 TBAF and Octylamine Treatment of InP/ZnSe/ZnS Quantum Dots(Sample AE)

19 mg of TBAF, 13 mg of didodecyldimethylammonium chloride, and 8 mg ofoctylamine were dissolved in 1.8 mL of toluene. Red-emittingInP/ZnSe/ZnS QDs (18 mg, 0.055 mL of a 325 mg/mL stock solution inoctane) with zinc oleate native ligands were added to this solution. Themixture was stirred at 70° C. for 120 min. The exchanged QDs wereisolated by precipitation with acetonitrile (0.6 mL) and redispersed inoctane (0.5 mL). The octane dispersion was used for opticalcharacterization.

Example 25 Octylamine Treatment of InP/ZnSe/ZnS Quantum Dots (Sample AF)

Didodecyldimethylammonium chloride (13 mg), and octylamine (8 mg) weredissolved in toluene (1.8 mL). Red-emitting InP/ZnSe/ZnS QDs (18 mg,0.055 mL of a 325 mg/mL stock solution in octane) with zinc oleatenative ligands were added to this solution. The mixture was stirred at70° C. for 120 min. The exchanged QDs were isolated by precipitationwith acetonitrile (0.6 mL) and redispersed in octane (0.5 mL). Theoctane dispersion was used for optical characterization.

Example 26 TBAF Treatment of InP/ZnSe/ZnS Quantum Dots (Sample AG)

Tetrabutylammonium fluoride trihydrate (57 mg), anddidodecyldimethylammonium chloride (39 mg) were dissolved in toluene(5.4 mL). Red-emitting InP/ZnSe/ZnS QDs (54 mg, 0.165 mL of a 325 mg/mLstock solution in octane) with zinc oleate native ligands were added tothis solution. The mixture was stirred at 70° C. for 120 min. Theexchanged QDs were isolated by precipitation with acetonitrile (1.8 mL)and redispersed in octane (1.5 mL). The octane dispersion was used foroptical characterization.

Example 27

Photoluminescent Properties of Nanocrystals after Fluoride and/or AmineTreatment and Electroluminescent Properties of Devices Prepared Thereof

The solution quantum yield, photoluminescence, and full-width athalf-maximum values of InP/ZnSe/ZnS quantum dots prepared with andwithout fluoride treatment are shown in TABLE 9.

TABLE 9 QY PWL FWHM Sample Composition Method (%) (nm) (nm) InP/ZnSe/ZnSZn(OA)₂ Native 87.5 616.4 43.7 Ligands AE InP/ZnSe/ZnS TBAF andOctylamine 86.5 616.4 42.2 AF InP/ZnSe/ZnS Octylamine Only 75.0 617.842.5 AG InP/ZnSe/ZnS TBAF Only 82.1 618.8 41.5

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. It will be apparent to persons skilled in the relevant artthat various changes in form and detail can be made therein withoutdeparting from the spirit and scope of the invention. Thus, the breadthand scope should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

1. A nanostructure comprising: a nanocrystal core; and at least oneshell disposed on the core, wherein at least one shell comprises ZnS andfluoride.
 2. The nanostructure of claim 1, wherein the core comprisesZnSe_(1-x)Te_(x), and wherein 0≤x<1.
 3. The nanostructure of claim 1,wherein at least one shell comprises ZnSe.
 4. The nanostructure of claim1, wherein the at least one shell comprises a first shell comprisingZnSe and a second shell comprising ZnS and fluoride.
 5. Thenanostructure of claim 1, wherein the fluoride is in the form of a metalfluoride, ammonium fluoride, or tetraalkylammonium fluoride. 6.(canceled)
 7. The nanostructure of claim 1, wherein the molar ratio offluoride in the nanostructure to zinc in the nanostructure is betweenabout 0.05 and about 0.35.
 8. The nanostructure of claim 1, wherein thenanostructure comprises: a core comprising ZnSe, and at least one shellcomprising ZnS and ZnF₂; a core comprising ZnSe, at least one shellcomprising ZnSe, and at least one shell comprising ZnS and ZnF₂; a corecomprising ZnSe_(1-x)Te_(x), wherein 0≤x<1, and at least one shellcomprising ZnS and ZnF₂; or a core comprising ZnSe_(1-x)Te_(x), wherein0≤x<1, at least one shell comprising ZnSe, and at least one shellcomprising ZnS and ZnF₂.
 9. A method of preparing the nanostructure ofclaim 1, comprising: (a) providing a nanocrystal core; (b) optionallyadmixing the core in (a) with a zinc source and a selenium source toprovide a core with a ZnSe shell; (c) admixing the core in (a) or thecore with a ZnSe shell in (b) with a fluoride source; and (d) infusing asolution comprising a zinc source and a sulfur source into the admixturein (c); to provide the nanostructure.
 10. A nanostructure comprising: acore comprising ZnSe or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and a firstmetal fluoride; and at least one shell disposed on the core, wherein atleast one shell comprises ZnS and optionally a second metal fluoride.11. The nanostructure of claim 10, wherein the first metal fluoridecomprises ZnF₂, HfF₄, or ZrF₄.
 12. The nanostructure of claim 10,wherein the second metal fluoride comprises ZnF₂, HfF₄, or ZrF₄.
 13. Thenanostructure of claim 10, wherein the molar ratio of fluoride in thenanostructure to zinc in the nanostructure is between about 0.05 andabout 0.35.
 14. The nanostructure of claim 10, wherein the nanostructurecomprises: a core comprising ZnSe and a metal fluoride comprising ZnF₂,HfF₄, or ZrF₄; and at least one shell comprising ZnS and a metalfluoride comprising ZnF₂, HfF₄, or ZrF₄; a core comprising ZnSe and ametal fluoride comprising ZnF₂, HfF₄, or ZrF₄; at least one shellcomprising ZnSe, and at least one shell comprising ZnS and a metalfluoride comprising ZnF₂, HfF₄, or ZrF₄; a core comprising ZnSe and ametal fluoride comprising ZnF₂, HfF₄, or ZrF₄; and at least one shellcomprising ZnS; a core comprising ZnSe and a metal fluoride comprisingZnF₂, HfF₄, or ZrF₄; at least one shell comprising ZnSe; and at leastone shell comprising ZnS; a core comprising ZnSe_(1-x)Te_(x), wherein0<x<1, and a metal fluoride comprising ZnF₂, HfF₄, or ZrF₄; and at leastone shell comprising ZnS and a metal fluoride comprising ZnF₂, HfF₄, orZrF₄; a core comprising ZnSe_(1-x)Te_(x), wherein 0<x<1, and a metalfluoride comprising ZnF₂, HfF₄, or ZrF₄; at least one shell comprisingZnSe; and at least one shell comprising ZnS and a metal fluoridecomprising ZnF₂, HfF₄, or ZrF₄; a core comprising ZnSe_(1-x)Te_(x),wherein 0<x<1, and a metal fluoride comprising ZnF₂, HfF₄, or ZrF₄; andat least one shell comprising ZnS; or a core comprisingZnSe_(1-x)Te_(x), wherein 0<x<1, and a metal fluoride comprising ZnF₂,HfF₄, or ZrF₄; at least one shell comprising ZnSe; and at least oneshell comprising ZnS.
 15. A method of preparing the nanostructure ofclaim 10, comprising: (a) admixing a solution of a zinc source, aselenium source, and a first metal fluoride source to provide a corecomprising ZnSe or ZnSe_(1-x)Te_(x), wherein 0≤x<1, and the first metalfluoride; (b) optionally admixing the core in (a) with a zinc source anda selenium source to provide a core with a ZnSe shell; (c) optionallyadmixing the core in (a) or the core with a ZnSe shell in (b) with asecond metal fluoride source; and (d) infusing a solution comprising azinc source and a sulfur source into the admixture in (a), (b), or (c);to provide a nanostructure.
 16. The nanostructure of claim 1, whereinthe nanostructure exhibits a photoluminescence quantum yield of betweenabout 60% and about 99%.
 17. (canceled)
 18. A device comprising thenanostructure of claim
 1. 19. A film comprising the nanostructure ofclaim 1 and at least one organic resin.
 20. A molded article comprisingthe film of claim
 19. 21. A nanostructure comprising: a nanocrystalcore; and at least one shell disposed on the core, wherein at least oneshell comprises ZnS or ZnSe; at least one fluoride bound to the surfaceof the nanostructure; and at least on amine bound to the surface of thenanostructure.
 22. The nanostructure of claim 21, wherein the corecomprises InP.
 23. The nanostructure of claim 21, wherein at least oneshell comprises ZnSe.
 24. The nanostructure of claim 21, wherein atleast one shell comprises a first shell comprising ZnSe and a secondshell comprising ZnS.
 25. The nanostructure of claim 21, wherein thefluoride is in the form of a metal fluoride, ammonium fluoride, ortetraalkylammonium fluoride.
 26. (canceled)
 27. The nanostructure ofclaim 21, wherein the molar ratio of fluoride bound to the nanostructureto zinc in the nanostructure is between about 0.05 and about 0.35. 28.The nanostructure of claim 21, wherein the nanostructure comprises ananostructure comprising a core comprising InP, at least one shellcomprising ZnS, at least one shell comprising ZnSe, tetraalkylammoniumfluoride bound to the surface of the nanostructure, and octylamine boundto the surface of the nanostructure.
 29. The nanostructure of claim 21,wherein the nanostructure exhibits a peak emission wavelength of between450 nm and 550 nm.
 30. (canceled)
 31. The nanostructure of claim 21,wherein the nanostructure exhibits a photoluminescence quantum yield ofbetween about 60% and about 99%. 32.-33. (canceled)
 34. A devicecomprising the nanostructure of claim
 21. 35. A film comprising thenanostructure of claim 34 and at least one organic resin.
 36. A moldedarticle comprising the film of claim
 35. 37. A method of preparing thenanostructure of claim 21, comprising admixing: (a) a nanostructurecomprising a nanocrystal core and at least one shell disposed on thecore, wherein at least one shell comprises ZnS or ZnSe; (b) at least onefluoride source; and (c) at least one amine source; to provide ananostructure. 38.-39. (canceled)